Radio system using nodes with high gain antennas

ABSTRACT

A radio communication route enables communication from an originating ground station to a destination ground station via one of multiple randomly orbiting satellites with no active attitude control. The ground stations and satellites include multi-feed parabolic antennas for receiving radio signals from and transmitting radio signals in multiple directions. The satellites store an address of a destination ground station from which an initial information signal is transmitted and antenna information identifying the satellite antenna feed on which the initial information signal was received. Plural satellite antennas transmit linking information identifying the satellite to the originating ground station. Data transmissions received at the originating ground station that designate a particular destination are transmitted by the originating ground station using the antenna on which the linking information was received and the satellite retransmits the data transmission using the satellite antenna feed identified by the stored antenna information.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to antennas for nodes in systemsautomatically establishing radio routes comprising radio links betweenground station nodes via one or more unguided or substantially unguidedaerial nodes such as satellites traveling in random or quasi-randomroutes, and more particularly, to antenna designs that increase theprobability of creating radio links between system nodes.

Description of Related Art

A brief history of certain aspects of cellular telephony relevant to thepresent disclosure is set forth in U.S. Pat. No. 5,793,842, which namesas an inventor Jerry R. Schloemer, who is also the present inventor. Oneearly system architecture, still in use today, involved a limited numberof tower-mounted transceivers (“drops”) and plural mobile radios(“cellular telephones”). In these early systems, and still in some casestoday, a central computer controlled communications between land linesconnected to the towers and the mobile radios. Implementing this systemarchitecture required significant investment in infrastructure andcomputing power, especially as the increasing popularity and technicalcapabilities of cellular telephones necessitated increased systemcapacity and sophistication. An alternate system architecture involvedusing radio transceivers (“nodes”) mounted on existing structures, suchas buildings and telephone poles. These architectures use nodes capableof receiving and transmitting signals to and from cellular telephonesalong a radio route among the nodes to drops at selected nodes. Thiscame to be called a mesh network, an early example being the systemdisclosed in Cox, Donald C., “Wireless Network Access for PersonalCommunications,” IEEE Communications Magazine (December 1992), pp96-115.

A particular challenge in implementing mesh systems was how to determinethe best available radio routes for interconnecting the nodes.Generally, early mesh systems still required a central computer to makerouting determinations, which added to system complexity and cost. Otherapproaches, such as that described in U.S. Pat. No. 4,937,822 to Weddleet al., involved a mesh system in which routes would be establishedautomatically, that is, without a central computer. However, Weddledisclosed such a system only in a mesh in which the nodes are laid outin a regular rectangular grid and radio routing links can only bebetween nodes orthogonally adjacent to each other (that is, cater-cornerlinks between nodes would not be permitted). The shortcomings of such asystem will be immediately apparent to those skilled in the art, if forno other reason than in a real-world setting it would be very difficult,if not impossible, to distribute nodes in a strictly orthogonal,uniformly-spaced rectangular grid over a wide enough area to make thesystem practicable. Moreover, Weddle does not disclose in detail anyalgorithm by which the nodes would actually create a preferred radioroute.

Against that background the present inventor's U.S. Pat. No. 5,793,842disclosed a system and method of creating radio routes through a mesh ofnodes that were not limited in their placement and did not require acentral computer. The systems and methods described in detail furtherbelow in connection with the present invention take advantage oftechnology described in U.S. Pat. No. 5,793,842 relating to the creationof radio routes through plural, randomly located nodes and thetransmission of communications using those routes. To avoid thenecessity of setting forth here the details of these types of systemsand methods, the disclosure in U.S. Pat. No. 5,793,842 relating to routecreation, and digital and analog signal transmission using the routesthus created, is incorporated herein by reference as if set out in full.

The inventor improved on that technology in his later U.S. Pat. No.6,459,899, which, among other things, describes a system that uses nodeswith directional antennas to improve the route creation andcommunication transmission capabilities of the earlier system. Thisimprovement solves complex issues presented by using nodes withdirectional antennas in the systems and methods described in the '842patent, and thus takes advantage of the higher quality radio linksachievable with directional antennas. The present invention also usesthe technology disclosed in the '899 patent, and its descriptions ofroute creation are incorporated by reference herein.

Before the inventor's approach to creating routes through a radio meshnetwork with randomly distributed nodes and no central computer, otherswere proposing ways to provide worldwide cellular coverage usingsatellites for call transmission between earth-based originating anddestination drops. An example of a satellite system that was actuallycommercialized is disclosed in various patents such as U.S. Pat. No.5,274,840 to Schwendeman and U.S. Pat. No. 5,410,728 to Bertiger et al.,both of which are assigned to Motorola, Inc. This system utilizedsatellites evenly distributed in a predetermined number of polar orbitsas transceivers for signals between satellites and between satellitesand transceivers on the ground. A sufficient number of satellites isused to provide coverage of the entire globe. However, in practice thissystem, which was commercialized by Iridium, had numerous drawbacks. Onewas that each satellite needed onboard thrusters, rocket fuel, andnavigational hardware to maintain its desired orbit. This increasedsatellite size and weight, which increased the launch cost, as well asincreasing the cost of the satellite itself. Also, to account forinevitable satellite failures, extra satellites would have to bemaneuvered into a failed satellite's orbit, thus increasing the cost ofthe entire system by requiring extra satellites and their concomitanthigh manufacturing and launch costs. See, for example, “IridiumSatellite Constellation,” Wikipedia,https://en.wikipedia.org/wiki/Iridium (last visited May 9, 2017).Ground-based orbit and attitude control using complex computertechnology further increased system costs. In the end, its drawbacksmade the system commercially unviable for mass market applications,although it is believed to have found use in specialized areas such asmilitary applications and reporting by journalists from remote areas.

In addition to maintaining each Iridium satellite in a particularorbital position relative to the earth and other satellites, theattitude of each satellite also had to be maintained within certaintolerances so that its antennas would be oriented for effectivesatellite-satellite and satellite-ground radio communications. One wayof providing attitude control was using onboard thrusters, which presentthe drawbacks already discussed. Various mechanically-based inertialattitude control systems have been proposed, such as those described inU.S. Pat. No. 3,017,777 and U.S. Pat. No. 8,164,294, and in Chabot, J.A., “A Spherical Magnetic Dipole Actuator for Spacecraft AttitudeControl,” Thesis for M. S. in Aerospace Engrg. Sciences, Univ. ofColorado, 2015. However, it is believed that these types of systemswould not perform any better than rocket-based attitude control, whiletheir mechanical complexity and onboard control systems would precludesignificant savings in weight as compared to rocket-based attitudecontrol.

The present inventor disclosed in his U.S. Pat. No. 5,566,354 asatellite cellular telephone system that improved on theMotorola-Iridium approach. The inventor's improved approach allowed thesatellites to occupy random orbits. This eliminated the orbital controlcomponents of satellite systems that relied on each satellite being in aknown location relative to the others, such as the Motorola-Iridiumsystem or the wireless telephone/satellite system disclosed in U.S. Pat.No. 5,303,286. However, the random-orbit system described in the '354patent has certain drawbacks, one of which is that the satellites stillrequire attitude control to insure that the satellite antennas point inthe correct directions. Nor, as discussed in detail further below, doesit have the advantages of a true mesh system, as that term is used inthis description.

Aside from the rapid spread of cellular telephone usage around the worldin recent years, access to the Internet through computers andsmartphones has become a necessity for businesses and individuals alike.It is difficult to do business or manage personal affairs effectivelywithout access to Internet-based resources like email, electronicbanking, investigative/search services, and many others. In addition,social media providers like Facebook and Twitter can only exist in areasof the world that provide Internet access. A satellite-based systempresents an ideal way of making the Internet and cellular telephoneservice available in remote areas without blanketing a country withtowers or installing land-based radio mesh nodes across vast areas.However, known satellite systems suffer from numerous drawbacks, some ofwhich are discussed above, and none has been successfully commercializedto date. In fact, a low-cost satellite system would have the potentialto replace tower-based systems and ground-based mesh systems altogether.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a radiocommunication system comprising a plurality of satellites capable ofestablishing radio links between orbiting satellites and between thesatellites and ground-based stations without requiring the satellites tobe maintained in predetermined orbits or in predetermined attitudesrelative to each other or the earth. In a preferred embodiment there area sufficient number of satellites to provide a satellite mesh thatensures almost to a certainty that any spot on the earth's surface willbe within sight of at least one satellite at all times. One specificembodiment utilizes at least 200 satellites.

One aspect of the invention rests in part on incorporating in each suchsatellite a plurality of antennas capable of transmitting and receivingin all directions. A radio link can be created when a radio beamtransmitted from an antenna in one satellite is received by an antennain another satellite. This is sometimes referred to herein as a “beammatch.” The inventor recognized that using a unique antenna arrangementand uniquely coded radio transmissions from the satellites and groundstations, and treating both as nodes in a mesh, would enable a radioroute to be established between ground stations by assembling radiolinks via one or more of the satellites. One insight that led to thisaspect of the invention is that the satellites' attitudes and relativepositions change sufficiently slowly as compared to the time that ittakes the on-board computers in each satellite to calculate a radioroute. Accordingly, once the radio route is established, communications(“calls”) between the ground stations via one or more of the satellitesare not normally disrupted or, in the event that an existing route isdisrupted as a satellite moves or tumbles, a new radio route can beestablished “on the fly” with the same or different satellites while thecall is in progress. As used in the description that follows, a “call”is a communication of content (digital or otherwise) over a radio routebetween satellites or between a satellite and a ground station, unlessotherwise indicated explicitly or by context. While not limited as such,the systems described herein are particularly well suited for thetransmission of data in packets, defined here in the generally acceptedsense as a collection of digital data with a portion representing thecontent of the transmission (sometimes referred to as the “payload”),and a control portion (sometimes referred to as a “header” or“trailer”), which contains information enabling the payload to bedelivered successfully, such as source and destination addresses, errordetection codes, and sequencing information.

In one of its more general aspects the present invention uses a uniquesatellite construction with on-board computers that can performcalculations and select antennas to create radio routes between groundstations via one or more satellites virtually in real time as thesatellites move in uncontrolled orbits with no attitude control. Theradio routes are determined by algorithms executed by the computers inthe satellites, so that a central computer is not needed to specifywhich satellite or satellites will comprise an optimum radio routebetween ground stations.

One embodiment of the invention uses the disclosed satellite mesh tocreate an optimum radio route that comprises a single satellite thatprovides a radio route between two ground-based transceivers. The uniquesatellite design described herein enables a single-satellite route to bemaintained even as the satellite tumbles with no attitude control or ifconditions change so that another satellite in sight of the ground-basedtransceivers will provide a better radio route because the firstsatellite drifted out of range or became inoperative for some reason.

A particular advantage of the system disclosed herein is that in apreferred embodiment it provides the above features and those describedin more detail below by blanketing the earth with lightweight,battery-powered satellites that reduce launch costs and eliminate thenecessity for complex and costly control systems for maintaining thesatellites in particular orbits and in particular attitudes. Anotheraspect of the invention uses ground stations with an antenna arrangementdifferent from that used in the satellites, since the limitations onsatellite weight, size, and power do not apply to the ground stations.This means that the ground stations can have a greater antenna density(more antenna beams over a given spherical area) and use antennas withmore power (gain), thus virtually ensuring that data communications willbe possible between any two ground stations.

Another embodiment of the invention enhances the ability of thesatellites to establish radio links between satellites and between asatellite and a ground station by using satellites that spin or rotateabout an axis. This increases the probability of creating a beam matchbetween two satellites because each satellite is likely to “see” moreantennas on other satellites during a given period of time. This enablesthe use of higher-gain antennas with correspondingly narrower beamwidths, thus increasing the strength of the radio links and thereliability of call transmissions. Typically, the satellites aredeployed with a predetermined angular velocity, which may be differentfor different satellites. In one variation of this embodiment, thesystem includes satellites that rotate in opposite directions. Furtherconsiderations for realizing this embodiment are discussed in thedetailed description that follows.

Yet another embodiment of the invention further enhances the ability ofthe system to establish radio links between system nodes (satellites andground stations) by using multi-feed parabolic antennas to transmitplural radio beams from each antenna over a prescribed spherical area.The antennas have larger reflectors than single-feed antennas used inother embodiments so that each radio beam has more gain. Although thesatellites according to the present embodiment will likely be larger andheavier than satellites with a comparable number of single-feedantennas, they will transmit a greatly increased number of high-gainradio beams available for creating beam matches representing higherquality radio links between system nodes.

Additional applications of systems and methods described herein relateto the incorporation of any of the node embodiments on various aerialvehicles other than low earth orbit satellites. These vehicles caninclude, without limitation, very low earth orbit satellites (100-200miles) that provide less signal attenuation of radio signals betweenthemselves and ground nodes and might be adaptable for use in systemsinterconnecting the so-called Internet of Things, high-altitude balloons(for example, 11 miles) that can be adapted for systems designed tobring Internet service to rural areas, and drones flying at 1000-2000feet that could increase the ability of the system to create radio linksdirectly with individual hand-held devices. In addition, an adaptationof the multi-feed antenna embodiment described above used in groundstations will increase the probably that radio links can be establisheddirectly between ground stations at varying elevations without involvingany aerial nodes.

These and other aspects and features of the invention and embodimentsthereof will be covered in more detail as this description proceeds.

This Summary is provided solely to introduce in a simplified form aselection of concepts that are described in detail further below. It isnot intended necessarily to identify key or essential features of thesubject claimed herein, nor is it intended to be used an aid indetermining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects of the invention will be better understood from the detaileddescription of its preferred embodiments which follows below, when takenin conjunction with the accompanying drawings, in which like numeralsand letters refer to like features throughout. The following is a briefidentification of the drawing figures used in the accompanying detaileddescription.

FIG. 1, comprising FIGS. 1A and 1B, schematically depicts the radio meshconcept disclosed in the inventor's U.S. Pat. No. 5,793,842 and U.S.Pat. No. 6,459,899.

FIG. 2, comprising FIGS. 2A and 2B, illustrates certain geometricprinciples underlying the space-based radio systems disclosed andclaimed herein.

FIG. 3 schematically depicts an embodiment of a satellite suitable foruse in the space-based radio systems disclosed and claimed herein.

FIG. 4 is a representation of various operational components of thesatellite depicted in FIG. 3.

FIG. 5 illustrates an embodiment of a process using a single satellitefor creating a radio route between two ground stations.

FIG. 6, comprising FIGS. 6A, 6B, and 6C, schematically depicts rotatingsatellites in accordance with an alternate embodiment of a system usingsatellites in random orbits

FIG. 7 is a schematic two-dimensional depiction of the surface of aspherical satellite having an antenna configuration in accordance withanother embodiment of the system described herein using randomlyorbiting satellites without attitude control.

FIG. 8 is a functional diagram of the electronic components of thesatellite with the antenna configuration depicted in FIG. 7.

FIG. 9 is a notional depiction of systems using various types ofnon-low-earth-orbit aerial vehicles, as well as showing a direct linkbetween ground stations incorporating the antenna configuration andcontrol circuitry depicted in FIGS. 7 and 8.

One skilled in the art will readily understand that the drawings are notstrictly to scale, but nevertheless will find them sufficient, whentaken with the detailed descriptions of preferred embodiments thatfollow, to make and use the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The detailed description that follows is intended to provide specificexamples of particular embodiments illustrating various ways ofimplementing the claimed subject matter. It is written to take intoaccount the level of knowledge of one of ordinary skill in the art towhich the claimed subject matter pertains. Accordingly, certain detailsmay be omitted as being unnecessary for enabling such a person torealize the embodiments described herein. It will also be understoodthat terms indicating direction or orientation may be used facilitatedescription. The use of such terms does not imply that the claimedsubject matter is limited to a particular orientation of the structurebeing described.

I. RADIO MESH CONCEPTS AND PRINCIPLES

The system described herein builds on certain principles underlying theuse of a plurality of transceivers (“nodes”) that can be used to formtermination points for links in a radio route using one or more of thetransceivers. Throughout the description herein, the term “radio,”“radio signal,” or the like is not limited to references toelectromagnetic radiation in frequencies commonly referred to as radiowaves. It is meant to encompass electromagnetic radiation of anyfrequency capable of transmitting information, including light,microwaves, VHF (“very high frequency”), UHF (“ultrahigh frequency”),etc. The discussion in this section describes certain relevant featuresof prior art arrangements sometimes referred to as mesh systems, andsome of the basic concepts that represent the significant advances overknown mesh technology achieved by the unique apparatus, systems, andmethods described herein.

A. Prior Art Mesh and Satellite Radio Communication Systems

Existing ground-based radio mesh systems such as those described in theinventor's U.S. Pat. No. 5,793,842 and U.S. Pat. No. 6,459,899 haveproven very effective in establishing radio routes for digital andanalog communication signals through a plurality of nodes. They arecapable of establishing high quality radio links in a mesh system thatallows nodes to be placed at convenient locations rather than in apredetermined pattern. FIGS. 1A and 1B illustrate such a ground-basedradio mesh. In this simplified example, communication signals CS can betransmitted between an originating node A and a nearby mobile radio (notshown), such as an Apple Inc. iPhone® or Samsung Electronics Co., Ltd.,Galaxy® so-called smartphone. Those signals must be in turn communicatedto a “drop,” such as a node B, which can be an Internet router or atelephone network, for example, connected to a land line. If the nodes Aand B are not in line-of-sight contact because of the presence of anobstruction between them, such as a large hill LH (FIG. 1A), a directradio link L may be subject to a severe reduction in signal strength, ifit is possible to establish a link at all.

As described above, many mesh systems proposed before those described inU.S. Pat. No. 5,793,842 and U.S. Pat. No. 6,459,899, used a centralcomputer to control routes between originating nodes and drops. However,the patents disclosed systems that utilized algorithms to enable thenodes themselves to establish a preferred route between as manyintermediate nodes as needed to optimize communications between anoriginating node and a destination node. For example, FIG. 1A shows asystem in which software and firmware in the nodes themselves establisha preferred route around the hill LH, comprising a radio link L1 betweenthe node A and a node X on top of a first high hill H1. The nodes use alink L1 between nodes A and X, even though the link actually leads in adirection away from the destination node B. The algorithms resident inthe individual nodes then establish a radio link L2 with another node Yon top of a second hill H2, and thence to the destination node B. Inthis preferred route, a node Z in the mesh, which may be part of a radioroute between two other nodes (not shown), is bypassed because the nodesX, Y, and Z self-determine that the preferred route is through the nodesX and Y.

One of the important features of this system is that the nodesthemselves can also create a different preferred route, say between thenodes X and Y through a node Z using links L4 and L5, if conditionschange after placement of the nodes. FIG. 1B shows how the nodesthemselves can create a different route between nodes A and B if thereis no clear line of sight between them. In this example, the line ofsight has been interrupted by a building BL constructed directly betweenthe nodes X and Y. Another example would be a tree that permits radiosignals to pass between the nodes X and Y during the winter because ithas no leaves, but disturbs a radio link in the summer when its leaveshave come out. In such a case, the systems described in U.S. Pat. No.5,793,842 and U.S. Pat. No. 6,459,899 enable the nodes A, B, X, Y, and Zautomatically to create a new preferred radio route using the new radiolinks L4 and L5 between the nodes X, Y, and Z.

These patents thus describe systems that use a mesh of nodes capable ofessentially random distribution in which the nodes themselves establishpreferred radio routes between destinations and drops using the onboardcomputational capabilities in the nodes to analyze radio signalsexchanged by the nodes. This eliminates the need for a central computerto communicate with the nodes and determine optimum or preferred routesusing data collected by the nodes from multiple other nodes in the mesh.Generally speaking, the only limitation on the placement of the nodes isthat intermediate nodes in a route of three or more nodes should bewithin sight of at least two other nodes. This allows the system tocover a wide area, and although it may require a large number of nodesto do so, as long as nodes can “see” each other the system will be ableto self-establish preferred radio routes.

However, it is not obvious how general concepts behind radio meshsystems comprising fixed-location, ground-based receiving andtransmitting nodes can be adapted to a system in which the nodes aresatellites orbiting the earth. The Motorola-Iridium system disclosed inU.S. Pat. No. 5,274,840 and U.S. Pat. No. 5,410,728 is more or less ananalog of ground-based systems with nodes in particular locations. Thatis, it requires the satellites to maintain predetermined orbits and haveonboard attitude control to keep the satellite antennas pointing in theright direction, and relies on knowing the locations of the satelliteswhen they receive a transmission from one ground station and retransmitit to another. While this approach works technically, it is believed tohave proved impracticable from a commercial standpoint because it wastoo costly to implement, although as noted above, it still has utilityin certain specialized applications. In addition, it uses a centralcomputer to establish radio routes among the satellites.

The inventor's U.S. Pat. No. 5,566,354 discloses a system usingrandom-orbit satellites, but as noted above, it is not actually a meshsystem as that term is used herein. For example, the system in the '354patent establishes a communication channel between ground-based mobileunits by having an originating unit send a page to a destination unit todetermine if a satellite is available for the purpose, and then simplytransmits communications between the two units through that satellite.The system does not have numerous salient features of the mesh systemdescribed herein, such as creating preferred radio routes using thequality of signals transmitted to and received by multiple nodes. Inaddition, the satellites still require expensive onboard attitudecontrol hardware such as positioning thrusters and rocket fuel for them,both of which add extra weight and thus increase the cost of deliveringthe satellites into orbit. The present system, on the other hand, usessatellites that continuously update the antennas in the nodes(satellites and ground stations) to enable a choice to be made as to theantennas at the nodes that will provide the highest quality radio linkbetween the nodes, whether they be satellites or ground stations. Inaddition, the '354 patent does not disclose how to providesatellite-to-satellite communications between randomly orbitingsatellites. And although the Motorola-Iridium system supportssatellite-to-satellite communications, its satellites have to maintainboth prearranged orbits and fixed attitudes.

B. Principles of the Unique Satellite Radio Mesh Systems DescribedHerein

The satellite radio mesh used in the present system supports radioroutes in which the preferred route between two ground stations includesmore than one satellite and having one or more satellite-to-satelliteradio links. It also supports radio routes that include a singlesatellite in communication with both ground stations. In bothembodiments a large number of unique satellites, described furtherbelow, are launched into orbit. The number of satellites is chosen toprovide a high probability that at any given moment, a point on thesurface of the earth will be within line of sight of a certain number ofsatellites. For example, U.S. Pat. No. 5,566,354 estimates that if 200satellites were randomly placed at an orbital altitude of 500 miles, agiven point on the earth would “see” on average over time about 12satellites, or stated another way, the chances of a given spot on theearth not being in the line of sight of at least one satellite is onlyfour in 1,000,000.

FIGS. 2A and 2B illustrate this principle graphically. The approximatedistance DH to the horizon EH from a satellite S at an altitude AL of500 miles can be calculated according to the formulaDH=[(R+500)²−R²]^(1/2), where R is the radius of the earth E. Dependingon the value chosen for R, DH is about 2000 miles. Thus, the area ofcoverage AR of a satellite is π×DH²≈12,500,000 sq. mi. Taking thesurface area of the earth as 197 million square miles, each satellitethus “covers” about 6% of the earth's surface, which means that onaverage any one point on the surface will “see” about 12 satellites(200×0.06). Conversely, the chance that a single satellite will not bevisible from any particular point on the earth is 94%. If there are 200satellites launched into random orbits, the probability that any givenpoint on the earth will not see at least one satellite is only0.94²⁰⁰≈0.0004% (that is, four in a million). The '354 patent includes atable, incorporated herein by reference, that shows the estimatedprobability of constant coverage over time of a point on the surface fordifferent numbers of satellites.

It should be noted that the term “random orbits” in the context of thepresent description must be considered in combination with the number ofsatellites used in the system. It generally means that a sufficientnumber of satellites are placed into orbits that are initially spacedapart with the goal of maximizing coverage of the globe. It is not meantto require random distribution in a pure mathematical sense. Rather, itis used to indicate that precise positioning of satellites at particularlocations is not required, and that the manner of placing them intoorbit will take into account the number of satellites comprising thesystem and the desired degree of certainty, calculated in accordancewith suitable statistical algorithms, that any given point on theearth's surface will be within sight of at least one satellite at alltimes. (It will be appreciated that the system permits differentsatellites to satisfy that requirement for a given point as thesatellites' orbits change over time.) For example, known techniques forgenerating so-called pseudorandom numbers can be used as a basis forcalculating initial satellite numbers and placement. Other ways ofachieving “random” satellite distribution are described in U.S. Pat. No.5,566,354 in the “Satellite Launch” section, which is incorporatedherein by reference. The number of satellites launched into orbit willpreferably be in excess of a calculated number to enable continued fullearth coverage by accounting for a certain number of satellite failuresover time, or for satellites that are destroyed by reentry into theearth's atmosphere because of orbit decay or damaged by space debris.

Another important feature of the system described and claimed herein isthat the satellites do not require active, onboard attitude control.Thus, they do not require any moving parts, mechanisms, or propulsionsystems, which reduces satellite weight and cost, and they can bereleased into orbit without regard to their angular orientation. It isexpected that satellites can deployed from a launch vehicle such as aspace station or the like. It will be preferable in some embodiments ofthe system described herein to attempt to deploy them with as littleangular velocity as possible, but no special effort is required in thatregard. Systems in accordance with such embodiments will create radioroutes even if the satellites “tumble,” meaning that each satellite canchange its angular orientation at a rate different from othersatellites, or not at all, as it orbits. Stated another way, thesatellites are neither in prescribed orbits nor in controlledorientations. It is possible in some implementations to distribute themass of the satellites and/or components comprising ferromagneticmaterials to maintain a certain amount of tumbling as they orbit theearth and interact with its gravitational and magnetic fields. Inaddition, the size and orientation of solar panels used to produceelectrical power (see FIGS. 3 and 4) can be judiciously selected toemploy the kinetic energy of photons striking the panels to provideforces that influence the tumbling motion of the satellites. If desired,each satellite can include tracking telemetry to detect when its orbitis decaying and it needs to be replaced, and to comply with any nationalor international protocols applicable to orbiting bodies. However, it isexpected that it will be relatively simple and inexpensive to providesuch telemetry.

In another embodiment the satellites are deployed in random orbits withan angular velocity imparted to them. In the manner described furtherbelow, this enables the use of higher gain antennas to create beammatches even though the radio beams may be narrower. This enhances theability of the system to more readily create radio routes using morethan one satellite, which has the potential in some settings to increasethe quality of the routes between ground stations and thereby facilitatedata transmissions. In still another embodiment, the satellitesincorporate parabolic antennas with multiple feeds to increase thenumber of high-gain beams potentially available for use as radio linksbetween system nodes. Details of these embodiments are described indetail further below.

II. SATELLITE DESIGN: ANTENNA CONFIGURATION AND ONBOARD CONTROLCIRCUITRY

The satellites according to one embodiment comprise system nodes thatutilize unique multiple antenna arrays and software-implementedalgorithms to create radio routes by enabling the nodes to nearlyinstantaneously identify an antenna transmitting information signals andan antenna in another node receiving information signals from thattransmitting antenna. Because the satellites and ground stations aregenerally equivalent vis-à-vis their function as nodes in the system,the term node can refer to both satellites and ground stations, unlessotherwise stated or the context indicates otherwise. In addition,software resident in each node uses content in the information signalsto evaluate the suitability of these antenna pairs as a radio linkbetween two nodes. Software resident in the nodes uses that evaluationto create a preferred radio route for sending data communications froman originating ground station to a destination ground station. Forpurposes of explaining basic concepts involved in creating radio routesusing the satellite system described herein, this discussion sometimestreats certain aspects of route creation separately. For example theconcept of identifying antenna pairs for potential radio links may bedescribed separately from identifying a preferred radio route selectingcertain links for a radio route. Nevertheless, it will be clear as thediscussion proceeds that route creation involves a combination of stepsthat begins when ground nodes send initial information signals andculminates with the creation of a preferred radio route forcommunication signals from an originating ground node through one ormore satellite nodes to a destination ground node.

The disclosed system and route creation process enables the use ofsatellites that drift in random orbits with no attitude control. Datacommunications can be transmitted and received even if the selected pairof antennas on the nodes changes over time, or if the satellitescomprising the route change over time. That is, computers onboard thesatellites and at the ground stations are capable of changing the radioroute during a given communication or from one communication to thenext. In addition, a radio route might utilize different satellitesduring a single communication. Or a first communication between groundstations at a first time could use a certain satellite or satellites,while a later communication between the same two ground stations mightuse one or more satellites not used in the first communication.

FIG. 3 is a schematic depiction of an embodiment of a satellite 10 thatcan be used in the space-based radio mesh systems described herein. Tofacilitate understanding of certain principles underlying the operationof the satellite 10 in the systems and methods described herein, it isshown with an outer casing 12 in the shape of a sphere centered at CT.Those skilled in the art will recognize that the satellite can have adifferent shape if so dictated by other design considerations. Certainfeatures of the satellite will be described with reference to acoordinate system having mutually orthogonal x, y, and z axes. It willbe understood as this description proceeds that one of the features ofthe space-based radio system disclosed and claimed herein is that thesatellite can assume any angular orientation as it orbits the earth, asalready discussed. It will be appreciated by those skilled in the artfrom the description thus far that the coordinate system shown in FIG. 3is used strictly for purposes of illustration in describing features ofthe satellite. Put another way, the coordinate system can be consideredto be tied to the satellite and to change its angular orientation withrespect to the earth as the satellite slowly tumbles.

The exemplary satellite 10 includes a plurality of antenna modules 12,one of which is depicted schematically in FIG. 3 for purposes ofillustration. Each antenna module in this example comprises adirectional antenna that transmits and receives radio signals at greaterpowers in predetermined directions. The present embodiment uses circulardish parabolic antennas each of which occupies a solid angle Ω, with avertex at the center CT of the spherical satellite. The number ofdiscrete antenna modules incorporated into the satellite will depend onthe particular application of the system and the antenna design. In oneembodiment Ω in steradians will be chosen so that a particular number ofantenna modules, distributed around the satellite, will be capable oftransmitting radio signals to and receiving radio signals from asufficiently large spherical area to enable radio signals to be receivedfrom and transmitted to ground station transceivers and antennas inother satellites to effect operation of the system in the mannersdescribed below. The actual configuration of the antenna modules 12 canbe determined using known antenna design principles to achieve thatgoal.

However, fundamental principles of antenna operation demonstrate thetechnical feasibility of equipping a satellite such as that depicted inFIG. 3 with a sufficient number of antennas to effect the system andmethods described herein. One design approach could specify that thebeam width of the antenna for each module must provide a certainprobability that signals transmitted from all of the antennas in aparticular satellite will be received at another satellite or aground-based transceiver. A typical manner of expressing beam width fora circular dish parabolic antenna is the angle α at which the power ofthe beam has decreased by 3 dB. This is referred to as the half-powerbeam width (HPBW) and is given by the relationship:

$\begin{matrix}{\alpha = \frac{k \times \gamma}{d}} & (1)\end{matrix}$where α is in degrees, k is a factor that depends on certain designparameters of the antenna and is typically assigned a value of 70°, γ isthe wavelength in centimeters, and d is the diameter of the circular“mouth” of the antenna reflector. Satellite Systems Engineering in anIPv6 Environment, Minoli, Daniel, CRC Press, Boca Raton, Fla. (2009),pages 78-80. For a 5 GHz signal, which is a common radio frequency(microwave C band) used in satellite communications, γ=6 cm (γ=c/f,where c=speed of light, 3×10¹⁰ cm/sec), so α≈140°, but it is not certainthat a radio beam transmitted by an antenna with a diameter d=3 cm, asdescribed in the inventor's U.S. application Ser. No. 15/656,111, filedJul. 21, 2017, would have sufficient energy. If the diameter were twicethe wavelength, which is more in line with conventional antenna design,the diameter of the antenna reflector would be 12 cm, making itsHPBW=35°. Under reciprocity principles, the same parabolic antenna wouldreceive signals arriving at 17.5° off-axis at −3 dB of its on-axis gain.

A satellite used in the present system will have to be large enough toaccommodate the various electronic and mechanical components requiredfor satellite operation, discussed below in detail in connection withFIG. 4, as well as being sufficiently robust in construction towithstand the stresses of launch and long-term exposure to the hostileenvironment it will encounter in orbit. The inventor's U.S. applicationSer. No. 15/656,111 describes a satellite perhaps as small as 20 cm indiameter, but a more practical goal at least for first generationsystems would be in the range of 60-70 cm, using antennas 12 cm indiameter with antenna feeds about two wavelengths from the antennareflectors. The opening at the surface of the satellite for each antennawill be a size that permits the beam from the reflector below thesurface to spread unimpeded. If the opening in the satellite is a circleabout 18 cm in diameter, its area is about 81π cm² (π×(9 cm)²). For asatellite about 60 cm in diameter, 25 such antennas will occupy about60% of the satellite surface.

It will be appreciated that satellites and antennas suitable for use inthe present mesh system can take different forms depending on trade-offsfamiliar to those skilled in engineering complex systems. As describedfurther below in more detail, one of the steps in creating a radio routeusing the embodiment of a satellite mesh described herein is thetransmission of identifying messages from all of the antennas in one ormore satellites and ground-based transceivers, which in certain contextsare referred to herein interchangeably as “nodes.” It will be seen thatincreasing the number of antennas in a node will increase the totalspherical coverage of radio signals transmitted from and received byother nodes, which in turn will increase the probability that a signalfrom one node will be received at another. it will be furtherappreciated that more antennas per satellite might make it possible toreduce the number of satellites placed in orbit. Such satellites mightbe more expensive and heavier, thus increasing launch costs, but otherfactors might offset the increased cost because fewer satellites mightneed to be launched. Those skilled in the art will also recognize thatthe system described herein can be implemented with satellites havingantenna arrays that transmit with less than full 360° sphericalcoverage.

By the same token, the increased weight of a ground station due toadding antennas is not a factor. Thus, a system might incorporatesatellites with fewer antennas than the ground stations. It might alsobe more feasible to design the satellites with a given number ofantennas and use statistical estimates to calculate the number of suchsatellites needed to ensure that a predetermined number is visible fromany given point on the earth's surface. After the satellites arelaunched into orbit, the system could be tested to confirm thecalculations and more satellites could added if desired. Moreover, thepresent example uses parabolic antennas to explain certain principlesinvolved in node design, but the system does not rely on using aparticular type of antenna. That is, the type of antenna and thespecific antenna design will also be factors in determining the beamwidth and number of satellites necessary to ensure to a suitableprobability that nodes will receive signals transmitted from other nodesat a useful gain. The factors that determine a successful design for anygiven implementation of mesh systems as described and claimed hereinwill be well understood by those skilled in the art. Certain antennaconfigurations described further below are uniquely designed to increasethe probability that a beam match will be created between any two nodes(satellite/satellite and satellite/ground station) in a system.

The satellite 10 also includes a plurality of solar panels, three ofwhich 14 a, 14 b, and 14 c, are shown in FIG. 3. In the illustratedembodiment the solar panels are oriented in mutually perpendicularplanes and spaced equidistantly around the satellite 10. For purposes ofdescribing the locations and orientations of the solar panels in thisembodiment, a satellite equator 16 is defined as the great circle wherethe satellite surface is intersected by a plane parallel to the x-yplane and passing through the center CT of the sphere. A zero meridian18 is defined as the great circle where the satellite surface isintersected by a plane parallel to the x-z plane and passing through thecenter CT of the sphere. And a normal meridian 20 is defined as thegreat circle where the satellite surface is intersected by a planeparallel to the y-z plane and passing through the center CT of thesphere. The solar panel 14 a is attached to the satellite by suitablemounting structure 22 a at the intersection of the equator 16 and thezero meridian 18. The solar panel 14 b is attached to the satellite bysuitable mounting structure 22 h at the intersection of the equator 16and the normal meridian 18. And the solar panel 14 c is attached to thesatellite by suitable mounting structure 22 c at the intersection of thezero meridian 18 and the normal meridian 20.

The solar panels are generally planar with solar cells distributed overone or both faces for generating electricity when the solar cells areexposed to sunlight. For maximum effectiveness, the planar solar panelsare mounted in mutually orthogonal planes to ensure that an adequatenumber of solar cells are exposed to sunlight regardless of the angularorientation of the satellite. In the depicted embodiment, the solarpanel 14 a lies in the x-z plane, the solar panel 14 b lies in the x-yplane, and the solar panel 14 c lies in the y-z plane. It will also beappreciated that the satellite includes three more companion solarpanels where the equator, zero meridian, and normal meridian intersecton the other side of the satellite. The companion solar panels (depictedwith a prime (′) in FIG. 4) are preferably oriented in the same planesas each of their counterparts 14 a, 14 b, and 14 c shown in FIG. 3. Eachsolar panel is preferably normal to the surface of the satellite so thatit does not obstruct the transmission and receipt of radio signals byantennas adjacent to the solar panels.

It will be appreciated that FIG. 3 is intended solely to illustratefeatures of the satellite 10 necessary to an understanding of thepresent embodiment of the satellite mesh system described herein. Thoseskilled in the art will understand that an actual satellite forimplementing the present system may have design features not shown inFIG. 3's schematic depiction. For example, good design practice maydictate that the mouths of the antennas be recessed below thesurrounding surface of the satellite to reduce the possibility of impactdamage by space debris. Or additional protection might be provided bycovering each antenna mouth (recessed or not) with a sheet of materialtransparent to signals transmitted by and received at the satellite. Thedesign and placement of the solar panels 14 shown in FIG. 3 is alsohighly schematic, and the invention disclosed and claimed herein is notlimited to any particular solar panel configuration, placement, or meansof deployment.

FIG. 4 illustrates schematically various components housed by thesatellite 10 (node) for creating a radio route capable of transmittingand receiving radio signals to and from other nodes. As those skilled inthe art will readily recognize, in the descriptions of this and otherembodiments and aspects of the radio systems comprising the subjectmatter disclosed and claimed herein, the control circuitry andcomponents described and depicted in the various figures are meant to beexemplary of any electronic computer system capable of performing thefunctions ascribed to them. Such a computer system will typicallyinclude the necessary input/output interface devices and a centralprocessing unit (CPU) with a suitable operating system and applicationsoftware for executing program instructions. In addition, termsreferring to elements of the system, and of the user interfacesdescribed herein, are used herein for simplicity of reference. Forexample, the terms “component,” “module,” “system,” “apparatus,”“interface,” or the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware (firmware), software, or software in execution, unless thecontext clearly indicates otherwise. For example, such a component maybe, but is not limited to being, a process running on a processor, aprocessor, an object, an executable, a thread of execution, a program,and/or a computer. By way of illustration, both an application runningon an electronic computing device and the device itself can be acomponent. One or more components may reside within a process and/orthread of execution and a component may be localized on one computerand/or distributed between two or more computers.

Referring in more detail to FIG. 4, the satellite 10 is depicted in aview in the x-z plane in FIG. 3. It will be appreciated that FIG. 4,like other depictions used herein to describe the subject radio systemsand their components, is not to scale. It depicts the solar panels 14 aand 14 c, as shown in FIG. 3, as well as the diametrically opposedcompanion solar panels 14 a′ and 14 c′ mentioned above. It alsoschematically depicts a plurality of antenna modules 12 a, 12 b, 12 c,12 d, 12 e, and 12 f, representing all of the antenna modules onboardthe satellite 10, for transmitting and receiving radio signals asdiscussed above in connection with FIG. 3. This schematic depiction isintended to convey the principle of operation of the present embodimentwhereby the plurality of antenna modules in combination will be capableof transmitting and receiving radio signals to and from a node insubstantially all radial directions. (However, as already noted, thesystem described herein can also be implemented with satellites havingantenna arrays that transmit with less than full 360° sphericalcoverage.)

The satellite 10 includes a power module 30 capable of providing areliable source of electrical power for operating the components of thesatellite. The power module 30 includes batteries that are charged bythe electricity generated by the solar panels. Suitable power regulatingequipment provides steady-state power to the various electroniccomponents carried by the satellite even though the solar panels willspend one half of each satellite orbit out of sight of the sun. Inaddition to the power module the satellite includes a central processingunit 40 with an operating system module 42 that stores operationalsoftware for controlling the various functions of the satellite. Asshown in FIG. 4, the CPU 40 is operatively connected to all of theantenna modules 12 via power and data links 40 a, 40 b, 40 c, 40 d, 40e, 40 f, etc.

FIG. 4 also illustrates four main operational modules under the controlof the operating system module. These components are likewise includedin ground-station nodes. Each satellite node in a radio routenecessarily uses two antenna modules. Since the satellites have nopreferred orientation, it is necessary for each satellite (node) toselect antenna modules 12 to communicate with another node, either asatellite or a ground station. An antenna pairing module 44 under thecontrol of the operating system uses information messages received fromother nodes (ground stations or other satellites) to pair an antennamodule in one node for transmitting/receiving signals with an antennamodule in another node for receiving/transmitting signals. The radiosignals exchanged between nodes are analyzed by a route creation module46 that uses algorithms discussed further below to create a radio routebetween two ground stations. (Ground station nodes have correspondingcentral processing units.) Once a radio route has been established, adata movement module 48 within each node controls the transmission alongthe radio route of communication signals CS (see FIG. 1). As suggestedabove, the illustration in FIG. 4 of separate modules for antennapairing and route creation does not necessarily imply that identifyingantenna pairs for transmitting/receiving signals between nodes andselection of potential radio links as a radio route are other than partof a more or less unitary process of creating a preferred radio routefor transmitting data communications from one ground station to another.

III. CREATING RADIO ROUTES FOR DATA COMMUNICATIONS

Launching sufficient numbers of the satellites 10 in random orpseudorandom orbits as discussed above enables implementation of avariety of route creation strategies. This section will discuss twoembodiments, and variations thereof, of radio routes created using sucha satellite system. One embodiment creates a radio route that comprisesradio links between a single satellite and two ground stations. Anotherembodiment, which allows for communications over longer distances,creates a series of one or more subroutes comprising a first groundstation, a first satellite and a second ground station, and anothersubroute comprising the second ground station, a second satellite, and athird ground station, and if necessary a third subroute comprising thethird ground station, a third satellite, and a fourth ground station,and so forth. This radio route would enable communications between afirst ground station and an n^(th) ground station using n−1 satellites.Variations on these embodiments are discussed below as well. Forexample, those skilled in the art will understand that a radio route canalso include satellite-to-satellite links if the computers resident inthe nodes assemble such a route based on the principles discussed below.

The ability to transmit data between ground stations using radio routesaccording to this embodiment of the present system is essentiallyconfirmed by the known operational capability of the Motorola-Iridiumsystem, which uses fixed satellites with attitude control. That type ofsystem was able to establish communication links directly betweensatellites and hand-held units on the ground in spite of the limitedantenna power (or gain) available in such units. Thus, an embodiment ofthe present system that uses antennas with limited power in thesatellites in combination with ground stations having more powerful,different type, and/or a greater number of antennas is virtually assuredof being able to establish radio routes between two ground stations.

In a basic embodiment, a satellite mesh system according to the presentinvention uses one of the satellites in accordance with the abovedescription to create a radio route for communications between twoground stations. This route involves two radio links, one between afirst ground node and a satellite node, and the other between thatsatellite node and a second ground node. Although the configuration of aground station may be different from that of the satellites,conceptually the transmission and reception of radio signals areprocessed by each essentially the same way. The creation of radio routesmay be enhanced by ground station nodes using more and/or more powerfulantennas, as well as different antenna types, as compared to thosecarried by the satellites, since the nodes on the ground do not have thesame constraints on weight, power, and space limitations as thesatellites. In addition, the ground station antennas can be mounted ontall buildings, towers, high hills, etc., to maximize line-of-sightvisibility with the orbiting satellites. In addition, the ground nodesonly transmit throughout a hemisphere, rather than in all sphericaldirections like the satellite nodes, thus reducing the cost of addingantennas for enhanced link creation.

A. Radio Route Creation and Maintenance

The principles underlying creation of radio links in the satellite meshsystems described herein will first be described by using a paradigm inwhich all transceivers, both satellites and ground stations, areconsidered to be nodes in the mesh. This will enable an understanding ofhow a radio route is created with more than one node-to-node link (thatis, with at least three nodes). Creation of a radio link betweensatellites or a radio link between a satellite and a ground station isin most relevant respects the same. Identifying and optimum radio linksand routes between pairs of nodes is in some ways analogous to themanner in which routes are created in the ground-based system describedin the inventor's U.S. Pat. No. 5,793,842 and U.S. Pat. No. 6,459,899.The description of link selection and route creation in those patents isincorporated herein by reference for background information regardingoptimum or preferred route creation by the nodes in a radio mesh.

An important difference, though, is that the present system, unlikethose known in the prior art, creates routes using nodes the positionsand orientations of some of which (the satellites) change over time.Accordingly, while prior fixed-node systems might occasionally have tochange a radio route for reasons discussed above in connection with FIG.1, they did not involve a dynamic environment with moving and tumblingnodes that required the system to be capable of automatically anddynamically updating the selection of transmitting/receiving antennapairs in the nodes as they move relative to each other and changeattitude. For example, Motorola-Iridium systems used satellites withfixed attitudes and known relative positions, thus making possibleoptimum route creation in a manner known for ground-based systems(although the Motorola-Iridium system is not known to use the nodesthemselves to create radio routes).

As just indicated, the present system and method for creating a radioroute with robust radio links between nodes involves selecting pairs ofantennas and estimating the “quality” of each link by criteria discussedbelow. An explanatory example will be described in connection with FIG.5, which shows a plurality of satellites with addresses no. 140, no.250, no. 280, no. 300, and no. 165, which can form radio links withground stations with addresses no. 1000, no. 1052, no. 1630, and no.2001. The following explains how the just the nodes in the systemdetermine a preferred radio route for data communications (calls) fromground node no. 2001 to ground node no. 1000 by choosing between twopotential routes, one via satellite no. 250 and the other betweensatellite no. 300. In a typical system there will be about 200satellites. The number of ground stations can vary, of course, but FIG.5 illustrates a few such ground stations over a wide area about, say,700 miles in diameter.

The link selection process is begun by transmitting from each groundnode a routing signal in the form of an initial information signalcomprising an identifying packet with the initial information. Theantenna modules in every node, both satellite nodes and ground nodes,are each given an identifying number. In addition, each node isidentified as either a ground node, sometimes referred to as type A, ora satellite node, sometimes referred to as type B. This node identifyingdata will typically be contained in a packet header, and the identifyingpacket will include a payload comprising an initial sample data stream.The following Table 1 is an example of digital first information signalstransmitted from two of the antenna modules in a first sending groundnode, say the node assigned address “1000.”

TABLE 1 Packet No. 1 Node address no. 1000 Node type: A Node antenna no.GA1 Link count: 1 Sample data (payload) XX . . . XX Packet No. 2 Nodeaddress no. 1000 Node type: A Node antenna no. GA4 Link count: 1 Sampledata (payload) XX . . . XXSimilar packets will be transmitted continuously from all of theantennas in all of the ground nodes. These signals will be received by anumber of other nodes, both ground stations and satellites, but theantenna pairing modules in the nodes will reject information signalssent from the same node type. The satellites also store the number oflinks back to the sending ground node. In this case, the link count isone.

The initial sample data stream will typically be a known sequence ofbits used to evaluate the quality of a potential radio link between twonodes in a manner described just below. It is anticipated that theantennas in each node can transmit the information signals at randomintervals without encountering interference with information signalstransmitted from other nodes. This is because the number of nodes, andthe number of antennas in a given node, that will receive signals fromother nodes will likely be small. Alternatively, the antenna modules inthe nodes can transmit information signals in preassigned time slots tominimize even further the possibility that an information signaltransmitted from one node will arrive at a given antenna in another nodeat precisely the same time that the given antenna is transmitting itsinformation signal.

Continuing with this example, the second step in the process involves anevaluation by all of the satellite nodes that receive initialinformation signals from the ground nodes. The process involves aplurality of operations carried out in the satellite antenna pairing androute creation modules. The antenna pairing modules in the receivingsatellites store the antenna on which it received the initialinformation signal. In the FIG. 5 example, satellite no. 250 storessatellite antenna SA6 associated with ground node address no. 1000, andsatellite no. 300 stores satellite antenna no. SA3 associated withground node address no. 1000. The route creation circuitry determines afigure of merit of the received initial information signal that reflectsa quality of the signal transmitted over that pair of antennas in therespective ground station and satellite. The figure of merit resultsfrom an analysis of certain parameters according to algorithms in thenodes, its purpose being to assign a quantitative value for ranking thesuitability of particular antennas in the two nodes as a radio link inthe radio route to be created between an originating ground station anda destination ground station. That is, this step in the process involvesranking the quality of a potential radio link between a ground stationsending an initial information signal and a satellite receiving it.Examples of properties of received signals that can be used to derive afigure of merit (signal quality) are one or more of signal strength, theerror rate in the data stream, and signal-to-noise ratio. In thisexample, the figure of merit ranges from one (worst quality) to 10 (bestquality).

The next step is for the route creation circuitry in all of thesatellites to send routing signals in the form of linking informationsignals from all of their antennas. To illustrate, assume that satellitewith address no. 250 receives an initial information signal from sendingground node no. 1000. Table 2 shows the linking information sent inpacket form from every antenna in node no. 250 vis-à-vis a potentiallink with sending ground node no. 1000:

TABLE 2 Transmitting from: Node No. 250 Node type: B Node transmittingantenna no. SA1 Node receiving antenna no. SA6 Linking node address no.1000 Linking node antenna no. GA1 Link count: 2 Link figure of merit(FOM) 6 of 10 Sample data (payload) XX . . . XXTable 3 shows the linking information sent in packet form from everyantenna in node no. 300 vis-à-vis a potential link with sending groundnode no. 1000:

TABLE 3 Transmitting from: Node No. 300 Node type: B Node transmittingantenna no. SA4 Node receiving antenna no. SA3 Linking node address no.1000 Linking node antenna no. GA10 Link count: 2 Link figure of merit(FOM) 3 of 10 Sample data (payload) XX . . . XXThe linking signals will not be accepted at other satellites, which arethe same type (type B) as the satellites no. 250 and no. 300 sending thelinking message. In addition, the ground nodes will be programmedlikewise to reject linking signals with a linking node address the sameas the receiving ground station, Note also that the link count fromTable 1 is incremented by one by the satellites, reflecting the numberof links (two) to the sending ground node no. 1000.

The antenna pairing circuitry in a receiving ground station thatreceives a linking signal stores at least the satellite node addressesfrom which the linking signals were transmitted, as well as the antennaon which the linking signals were received at the receiving ground node.In FIG. 5, the ground station no. 2001 stores satellite address no. 250associated with antenna no. GA5, and satellite address no. 300associated with antenna no. GA21. The receiving ground node alsodetermines respective figures of merit for potential links betweenitself and satellite no. 250 and between itself and satellite no. 300.In this example, the FOM=6 for a potential link between ground stationNo. 2001 and satellite no. 250 and FOM=8 for a potential link betweenground station No. 2001 and satellite no. 300.

A preferred radio route between from the receiving ground station to thesending ground station is then determined based on the figures of meritof the available potential links. In the example shown in FIG. 5, thetotal figure of merit for the radio route via satellite no. 250 is 12(6+6) and the total figure of merit for the radio route via satelliteno. 300 is 11 (3+8). Therefore, the preferred radio route is viasatellite no. 250. Note that it is the quality of the overall route thatdetermines the choice, not the quality of an individual link. Asdescribed in more detail below, a data transmission destined for thesending ground station no. 1000 includes the destination address (nodeno. 1000). The receiving ground station no. 2001 knows that the firstradio link in the route to destination node no. 1000 is satellite no.250 and that a transmission on antenna no. GA5 of ground station no.2001 will be received at satellite no. 250. (Optionally, the satelliteno. 250 can confirm that the transmission is from ground node no. 2001if the transmission is received on satellite antenna no. SA1.) Satelliteno. 250 has stored antenna no. SA6 as the antenna to use for datatransmissions to ground station no. 1000. (Optionally, the groundstation no. 1000 can confirm that the transmission is from satellite no.250 if the transmission is received on ground station antenna no. GA1.)Thus, the selected antennas at the ground stations and the satellite(the nodes) direct transmission signals from an originating node to asatellite and then to a destination node without requiring that theentire route being stored at any one node or central location andwithout requiring a central computer to determine a preferred route.From this example, one skilled in the art will understand how radioroutes are constructed for data communications from any of multiplereceiving (destination) ground stations to any of multiple sending(originating) ground stations.

It will also be understood that the satellites no. 140, no. 280, no.165, etc., may also receive initial information signals from the groundstation no. 1000 and send linking signals that are received by groundstations no. 1052, no. 1052, no. 1630, and no. 2001. Likewise, all ofthe satellites shown in FIG. 5 and any others within radio range (seeFIG. 2) may receive initial information signals from all of the groundstations no. 1052, no. 1630, and no. 2001, and any others within radiorange. However, the determination of a preferred route between any twoground stations proceeds according to the above discussion, in which thecombined figure of merit of both potential links in a radio routebetween the ground stations is evaluated by the receiving ground node ofa potential radio routes.

The above steps are continuously repeated at predetermined intervals,including during the transmission of packets of communication signalsover a radio route. Thus, as the satellites move and change orientation,the modules in the nodes can continuously update the evaluation of theradio links between nodes, and can change the preferred radio routebetween originating and destination nodes. This is facilitated by thefact that each node actually only communicates with a limited number ofother nodes and thus only a limited number of links has to be updatedwith each iteration of the link creation process. The frequency of thelink refreshing process will depend on various factors, but it isbelieved that frequencies between 0.5 and 20 Hz will be adequate in atypical system. As already noted, the link selection and maintenanceprocedure is performed by computations solely using the onboardcalculating capacity of the nodes as described herein.

It should be also noted that one node might receive a signal fromanother node on more than one antenna, depending on the properties ofthe antenna modules, such as their HPBW. However, the route creationprocess is the same as described above in that instance. It will also beappreciated that many different criteria can be used to evaluate thequality of the potential link between the nodes. Typical ones would bedirect indications of link quality such as the strength of the receivedsignal and the error rate estimate. However, other criteria can be usedas well. For example, the amount of remaining battery life in each ofthe nodes in the potential link could be determined and the qualityrating (figure of merit) adjusted to account for how long a satellitehas been exposed to the sun as an indication that battery power mightonly remain strong enough to support a link for a short time. Anothercriterion could be link loading, which refers to the number of potentialradio links with other nodes that is stored at a particular node. Eachnode in the system (ground stations and satellites) can eliminatepotential links with a quality below a predetermined threshold (sayFOM=2). This will prevent a route from being formed using one very highquality link and one very low quality link, the latter of which maydisrupt data communications even though the overall quality of the routeappears to be satisfactory. It may also reduce the time required todetermine a preferred a radio route by eliminating a number oftransmissions between the nodes.

B. Transmitting Data Communications Over the Radio Route

As just explained, once a plurality of links is assembled into a radioroute, it can be used to transmit communication signals from anoriginating node to a destination node. However, one issue that must beaddressed when communicating data transmissions over the radio route isthat a single antenna in a node cannot both transmit and receive signalssimultaneously. This issue is addressed in a variety of ways in the '842and '899 patents. One that is particularly adapted to the present systemis the designation of the nodes as one of two types, called “A” and “B”in this description (or “odd” and “even” in the '842 and '899 patents).In such an arrangement signals transmitted from one type of node areseparated in some fashion from signals transmitted from the other typeof node so that a node can receive signals on the same antenna that ituses for transmitting signals.

One way of doing this is for one type of node to transmit in certainfrequency bands and the other type to transmit in different frequencybands. In this arrangement an antenna in a node can transmit and receivesignals at the same time. One drawback is the necessity of providingsufficient separation between the respective frequency bands to ensurethat the there is no interference when an antenna is transmitting andreceiving at the same time. Another way of separating signaltransmission and reception is to transmit from one type of node in aparticular time slot and from the other type of node in a different timeslot interleaved with the first time slot.

Data/communication signal transmission in accordance with thisdescription is controlled by the data movement modules 48 in thesatellites 10. For example, a data communication comprising packets ofdata with a header and a payload will be received at an originatingground station. The header will typically include address information,including identification of the destination ground station. The datatransmission module unpacks the address information and indicates thesystem address (node number) of the destination node. The packets willthen be sent to the destination ground station over the radio routeestablished in the manner described above. An important aspect of thepresent system is that the preferred radio routes are subject to changeeven during an ongoing data transmission. However, the data packetsarriving at the destination ground station can be unpacked, undergoerror correction, and be reassembled in the proper order in accordancewith known principles, even if the packets arrive out of order becausethey traveled via different routes or were delayed while a differentroute was being created.

C. Summary

It will be apparent to those skilled in the art that the present systemis not simply a superposition of the route creation techniques describedin the '842 and '899 patents on a three-dimensional mesh in which thenodes include satellites instead of fixed devices in an essentiallytwo-dimensional space. There are numerous factors that go into linkselection and route creation, some of which are discussed above, thatmust be accounted for in the type of space-based, three-dimensional meshdescribed herein. For example, since the satellites have differenttrajectories, some of which will pass over large expanses of unpopulatedoceans, while others will pass over land masses that will generate moredata transmissions, battery life can vary greatly from satellite tosatellite. Accordingly, the amount battery charge remaining can be animportant parameter in selecting a satellite as a node in a radio route.

The use of a single satellite to establish an optimum or preferred radioroute has several advantages. One is that it identifies a preferredroute virtually instantaneously because the radio signals passed betweenthe satellites and the ground stations include information that is usedby algorithms stored at the ground stations and in the satellites tocalculate a preferred radio route in small fractions of a second. Thus,as soon as a ground station transmits a signal indicating that a routeis needed to another ground station, the route can be establishedimmediately and used for transmitting communication signals. This typeof three-node route can “refresh” sufficiently rapidly to minimizedisruptions of data transmissions so that if at a later time a differentsatellite, or different antennas on the same satellite, would provide abetter quality route, the route configuration can be adjusted nearlyinstantaneously to provide better quality links and minimize delays indata transmission. It also allows for changing the satellite used in theroute for other reasons, an example being waning battery life.

Those skilled in the art will understand that engineering a system inaccordance with the above description will require trade-offs amongdifferent aspects of the system. Thus, an actual system will likelyinvolve many competing considerations in optimizing a particular design.Some of these considerations are the number of satellites, satellitealtitude, the number of antennas, particularly in the satellites, thebeam width of the antennas, the size of the satellites, the cycle timefor updating route creation, just to name a few.

An aspect of the present embodiment is that the probability of therebeing at least one satellite present to establish aground-to-satellite-to-ground radio route can be readily increased bysimply placing more satellites in orbit, in accordance with thedescription above. Since the satellites are very light and inexpensive,increasing their number is an economically feasible way of increasingthe reliability of the system. Although there may be periods when thereis no satellite immediately available for the establishment of a radioroute between two ground stations, the rapid rate at which the systemcan refresh itself increases the probability that at least one satellitewill soon (likely within a few seconds) become available. In mostapplications, a time lag with a duration of this order of magnitude willbe acceptable. For those reasons, a particularly useful application ofthe present embodiment is providing reliable radio routes overparticular geographic areas.

The system described herein also enables use of the randomly orbitingsatellites to create a ground-to-single-satellite radio route over whichsignals can be transmitted and received only over a predeterminedgeographical area. The inventor's U.S. application Ser. No. 15/656,111,filed Jul. 21, 2017, describes such a system employed to provide radioroutes throughout Egypt. The system is also is readily adapted tosettings where ground nodes are too far apart, or where topographicalfeatures will severely limit the number of satellites visible to bothground nodes. In that case one or more intermediate ground nodes areprovided between the distant locations to create multiplesingle-satellite radio routes. Such a system used to provide coverage ofthe entire Russian Federation. These and still further embodiments andaspects of the invention are described in U.S. application Ser. No.15/656,111, and in the inventor's U.S. provisional applications No.62/379,601, filed Aug. 25, 2016, and No. 62/396,181, filed Sep. 18,2016, the contents of all three of which are incorporated herein byreference as if set out in full.

IV. ROTATING SATELLITES

As already discussed, designing a satellite-based radio mesh system inaccordance with the above description involves myriad trade-offs among awide variety of parameters. Two particular parameters that work at crosspurposes, and thus require judicious selection, are the beam widths ofrouting signals and calls transmitted by the antennas in the nodes andthe power (gain) of the antennas. On the one hand, greater beam widthwill increase the probability that a beam match can be created, but agreater beam width reduces the gain of the antenna. Conversely, anarrower beam will increase antenna gain, but reduce the probability ofcreating a beam match between nodes. This trade-off is particularlysignificant in the satellite nodes because the satellite antennaconfiguration has to take into consideration constraints on the weightand size of the satellites, which limits the number of antennas thesatellite can carry, and on the electrical power available from onboardbatteries. It is also desirable to increase the number of possible beammatches between nodes because some radio beams may be weakened bygrazing the earth's surface, which can partially block the signal beforeit reaches a receiving node.

Achieving the proper trade-off between beam width and antenna gain isimportant to the efficient functioning of a random-orbit satellitesystem. Such a system relies on the statistical probability that routescan be created using randomly orbiting satellites to create and selectroutes. A basic system that is simple and inexpensive to implement, andis especially effective in creating single satellite radio routes, usestumbling satellites as discussed above. As already described, thesatellites' antennas point out into space—towards each other and theearth—to enable the establishment of links between nodes. A fundamentalproperty of the system is its dependence on routing signals and datatransmissions of sufficient strength reaching other nodes (groundstations and satellites). The system relies on having enough satellitesin orbit and making the proper design trade-offs, including beam widthvs. gain, to enhance the probability that a suitable route can becreated between two ground stations via one or more satellites. However,there may be system installations in which better data transmissioncould be achieved by a multiple satellite route if the probability ofcreating high quality (figure of merit) links between satellites isincreased.

The present embodiment utilizes satellites that rotate about an axis,which, as explained herein, increases the likelihood that a route withhigh quality links and sub routes can be created using one or moresatellites. As explained below, employing rotating satellites enablesbeam width to be reduced, with a corresponding increase in gain, therebyresulting in higher quality radio links between nodes.

A. Principles Underlying the Present Embodiment

In the tumbling satellite embodiment discussed above, an exemplarysatellite configuration uses 25 antennas covering about 60% of thesurface of a spherical satellite. Thus, a rough estimate of theprobability of a radio beam transmitted by such a satellite beingreceived by another like satellite would be about 36% (0.6×0.6). It willbe appreciated by those skilled in the art that this is only anestimate, since the radio beams will have side lobes that will increasethe probability that a link will be created to a certain extent. If thediameter of the satellite is doubled, the diameter d of the parabolicdish antennas used in the above-described example can also be doubled.By above equation (1), α=(k×y)/d, the HPBW will be halved, to about 18°,from the value of the antenna example given above. While the area of thebeam will be only ¼ as large, the antenna gain will be increased by afactor of four, or about 6 dB. On the other hand, the probability of aradio beam transmitted from one tumbling satellite being received byanother is reduced to about 2% (36%×(¼)²).

As discussed above in the tumbling satellite embodiment, repeated radiosignals sent by nodes in the system include information on links and subroutes that need only include the address of a final ground destinationand a figure of merit to that destination. The rotating satelliteembodiment takes the tumbling satellite embodiment as a point adeparture toward a technique for increasing the likelihood of creating aradio link, especially between satellites with high-gain, narrow-beamantennas. It will be appreciated, particularly from the discussion thatfollows, that a particular radio route in a spinning satellite systemmay not last as long as in a tumbling satellite system. Accordingly, oneway to enhance the route creation process would be to use route creatingsignals that have a smaller amount of sample digital data (see Tables1-3, above) to enable them to be transmitted in a shorter period of timeto effect more rapid route creation.

As also discussed above, data transmissions (“calls”) will typically bein the form of packets with a header, which includes address dataindicating the packet destination, and a payload comprising the contentof the transmission. Header information in multiple packets can be usedto arrange the packets in the same order in which they were transmitted.Although a particular radio route in a rotating satellite system may notlast as long as in a tumbling satellite system, the data transmissionpacket headers will include information on the proper order of thepackets for use by the destination ground station to reassemble thetransmission. Thus, while there may be delays in completing a particulardata transmission while a new radio route is created inmid-transmission, that potential drawback will be offset by the factthat the higher gain radio beams made feasible by using rotatingsatellites will be more likely to establish radio routes by which datatransmissions between certain ground stations can be made in the firstplace.

B. Linking Satellites to Satellites

The discussion further above of the tumbling satellite embodiment pointsout that the establishment of radio links between ground stations andsatellites can be enhanced by increasing the number and gain of groundstation antennas. This is feasible in most installations because groundstations typically do not have the constraints on weight, availablespace, and electrical power that exist with the satellites. In thepresent embodiment the establishment of radio links by beam matchingbetween satellites is enhanced by using satellites that are deployedinto orbit deliberately spinning about a rotational axis. In oneembodiment, the satellites themselves have the same components as thesatellite depicted in FIGS. 3 and 4 and described in the text aboveassociated with them.

The angular velocity of the satellites will be relatively high. Forpurposes of illustrating the operation of a typical system usingrotating satellites, it will be assumed that the satellites are deployedwith an angular velocity ω=2π rad/sec (60 rpm). Those skilled in the artwill understand that this example is not meant to be limiting and thatit is within the scope of this disclosure to employ any angular velocityeffective to establish radio routes as described and claimed herein. Theorientation of the axis of rotation will not be controlled, butprinciples of physics dictate that each satellite will assume an axis ofrotation through its center of mass and the axis of rotation willprecess around the angular velocity w. However, the orientation of theaxis of rotation at any given time does not affect the creation of radiolinks, as will be apparent from the discussion that follows.

Rotating satellites increase the probability of a transmitted radio beambeing received by another satellite because the satellite antennas“sweep” an area as the satellite rotates. This can be understood byconsidering the satellite S₁ shown in FIG. 6A, which is schematiccross-section through the satellite “equator,” corresponding to theequator 16 of the satellite 10 in FIG. 3. In this example, the satelliteS₁ comprises five antennas 12 ₁, 12 ₂, 12 ₃, 12 ₄, and 12 ₅, each havingan HPBW of 35°, arranged equally around its equator 16 and rotatingabout the z-axis at an angular velocity ω. A location RL remote from thesatellite and lying in the plane of the equator will “see” five antennasas the satellite rotates through one complete revolution. It will beunderstood that this number will be different for locations not in theequatorial plane, but the principle still holds. It will also beappreciated that the number may increase or decrease because ofprecession about the rotational axis, but most locations remote from thesatellite (including ground stations) will still see plural antennas asthe satellite rotates. Thus, a second satellite with its equatorialplane in the equatorial plane of the first satellite S₁, the probabilityof being able to create a radio link with a 6 dB gain increase over thetumbling satellite example above is about 10% (5 antennas×2% for eachantenna). The probability of creating a beam match with a ground stationantenna is likewise increased.

It will be understood that this is a highly idealized representation,which ignores factors such as precession of the satellites around theiraxes of rotation, but it nevertheless illustrates the concept thatrotating satellites present an increased probability for the creation ofbeam matches between two satellites. Nevertheless, considering the largenumber of randomly orbiting satellites available for route creation, theincreased probability of beam matches using rotating satellites will inmany, if not most, cases be sufficient to enable assembly of a radioroute with higher quality links between two ground stations via multiplesatellites. While this will have special applicability in reachingground stations separated by large distances, it also can increase thereliability of radio routes between ground stations in other settings.

1. Counter-Rotating Satellites

The satellites are preferably deployed with about half of them rotatingin a first direction about their rotational axis and the other halfrotating in the opposite direction. FIG. 6B, which uses like numeralsfor like parts in FIG. 6A, illustrates this principle by showing thesatellite S₁ rotating at an angular velocity ω in a first direction anda second satellite S₂ rotating at the same angular velocity −ω (in theopposite rotational direction). This illustrates how a beam matchbetween antenna 12 ₅ in satellite S₁ and antenna 12 ₄ in satellite S₂will be sustained longer than if the two satellites were rotating in thesame direction. That is, if the satellites are rotating in oppositedirections, facing antennas on the satellites are traveling atessentially the same linear velocity relative to each other. On theother hand, if the satellites are rotating in the same direction, theirrelative linear velocity is twice the linear velocity of each. With asufficient number of satellites in orbit (200 in the previousembodiment), it is believed that there is a significant probability ofhaving a plurality of counter-rotating satellites over any givengeographic area for which a radio route is being established. Thus, thelikelihood of quickly establishing a relatively long-lasting radio routeis increased by deploying at least some, and preferably about one-half,of the satellites rotating in the opposite direction from the others. Inaddition, not only are two antennas on respective satellites inalignment longer, but as soon as they rotate out of view of each other,two other antennas of the satellites may align, thus enabling rapidrefreshing of the radio link between the satellites. In the exampleillustrated in FIG. 6B, antenna 12 ₁ in satellite S₁ and antenna 12 ₅ insatellite S₂ will align next.

Like the example used to illustrate the increased efficacy of usingrotating satellites discussed just above, this is also an idealizeddescription of how counter-rotating satellites can create longer lastingradio links between them. In addition, to the assumptions underlying theabove description, there may not be at any given time twocounter-rotating satellites over an area where α radio route is desiredbetween two ground stations. Nevertheless, taken together, theseexamples illustrate the point that rotating satellites, and particularlycounter-rotating satellites, will provide a sufficient probability ofestablishing a relatively high gain radio link between the random orbitsatellites to enable reliable data communications between two groundstations via one or more satellites. And because the antennas point in aplurality of directions (preferably over the entire spherical spacesurrounding the satellite), the opportunity for establishing a radiolink between two spinning satellites will in most instances be enhancedby using rotating satellites.

2. Satellites with Different Angular Velocities

A variation of the embodiment described just above employs satellitesthat rotate at different angular velocities. This variation is depictedschematically in FIG. 6C, in which the satellite S₁ rotates at anangular velocity ω₁ and S₂ rotates at a different angular velocity ω₂.The advantage of this system is that the antennas on thecounter-rotating satellites may be out of phase in the sense thatantenna on one satellite may be pointing directly to a space betweenantennas on a second satellite, as depicted in FIG. 6C. If thesatellites are rotating at the same angular velocity, this situation canpersist for an extended period of time, thus weakening a radio linkbetween the satellites, or perhaps preventing the establishment of alink altogether. Rotating the satellites at different angular velocitieswill increase the likelihood that at some angular position antennas onboth satellites will face each other (be in phase), thus enabling theestablishment of a useful radio link between them. For example, in thecase illustrated in FIG. 6C, the antennas on the satellites are exactly180° out of phase, in that the antenna 12 ₂ on satellite S₁ is pointingdirectly at the space between the antennas 12 ₄ and 12 ₅ on satelliteS₂. If ω₁=1.33×ω₂, the antenna 12 ₅ on satellite S₂ and the antenna 12 ₅on satellite S₂ will line up as the satellites rotate.

It is anticipated that certain installations of the system will utilizenumerous satellite to satellite links, while at the same time being ableto tolerate some delays transmitting calls between ground stations. Thistype of installation can benefit from using satellites that rotate atslightly different angular velocities. In other words, the system wouldbe designed to increase the probability that a satellite transmitting aradio signal would rotate at a different angular velocity than asatellite receiving the signal. The data communications might be delayedwhile the radio route is intermittently disrupted and refreshed asdifferent antennas on the two satellites disalign and realign. However,this can be compensated for by buffering the data communications andsending them each interval when the radio link is present.

In an exemplary approach, the cohort of satellites could be divided intofive groups with different angular velocities in accordance with thefollowing table.

TABLE 4 Very slow spinner: 0.68 revolutions per second Slow spinner:0.84 revolutions per second Average spinner: 1.0 revolution per secondFast spinner: 1.16 revolutions per second Very fast spinner: 1.32revolutions per second

The discussion immediately above explains how this can tend to increasethe probability of establishing beam matches between the antennas onrespective satellites. That is, the above discussion demonstrated oneinstance of how a satellite rotating at an angular velocity 1.33 timesthe angular velocity of another can facilitate a beam match. The sameprinciple applies for other multiples of angular velocity.

By the same token, this system implementation will also make more beammatches possible in a given time period because the antennas on onesatellite will have more opportunities to line up sufficiently withantennas on another satellite to form beam matches if the satellites arecounter-rotating at different angular velocities. There may be no beammatches between two satellites at a given time, or for a certaininterval, as they rotate. However, as they continue to rotate atdifferent angular velocities, antennas on the satellites will likelyform beam matches because antennas on the respective satellites will belikely to line up at some point. This may take plural revolutions of thesatellites, but rotation at different angular velocities greatlyincreases the probability that many more matches will be created as thesatellites continue to rotate. It will thus be appreciated from thecomplex interrelationship of the antennas on different satellites as thesatellites move in their orbits and rotate about their axes thatproviding plural cohorts of satellites rotating at respective differentangular velocities will increase the probably of creating more beammatches between pairs of the satellites during any given time interval.Any resulting delays while beam matches are created may be tolerable ifthe alternative is an inability of a particular ground station to sendand receive data transmissions at all.

3. Other Considerations

It is known that the angular velocity of a body rotating in earth orbit,especially at lower altitudes, is subject to decay from a number offactors. For example, even though the earth's atmosphere is extremelythin at low-earth orbital altitudes, the region in which satellites usedin the present system will preferably occupy, orbiting objectsnevertheless still experience aerodynamic drag. Forces generated by thepassage through the earth's magnetic field of ferromagnetic materials inthe object can also affect the angular velocity of a rotating body suchas a satellite. The tendency of the rotating satellites to undergo areduction in angular velocity over time can be compensated for in avariety of ways. One is to use retro rockets or active mechanicaldevices known in the prior art. However, since one of the objects of theinvention is to minimize the cost of building, deploying, andmaintaining the satellites used in the radio systems described herein,it is preferred to use passive means for compensating for externalforces on the satellites or for creating forces to control satellitemovements.

One such means uses solar panels with solar cells only on one side toutilize the momentum of photons striking the panels to create a torqueabout the rotational axis of the satellite. For example, referring toFIGS. 3 and 4, for a satellite that is deployed to rotatecounterclockwise about the z-axis (as viewed in the negative-zdirection), each solar panel 14 a would have solar cells only on oneside, namely the side facing the viewer for the solar panel 14 a to theright in FIG. 4 and the side facing away from the viewer for the othersolar panel 14 a to the left in FIG. 4. The remaining solar panels wouldstill have solar cells on both sides. Although larger solar panels willincrease aerodynamic drag on the satellite, it is believed that it willbe possible through judicious design to provide solar panels of a size,configuration, and orientation that will generate a net torque on thesatellite that overcomes the tendency of the angular velocity to decay.

It is likewise believed possible to selectively distribute the mass ofthe satellite components to cause it to rotate about a particular axis.Since it is anticipated that the battery will form a large proportion ofthe satellite mass, it will preferably be located at the center of massof the satellite and have a mass distribution that is symmetric aboutthe axis of rotation. In addition, the effects of the earth's magneticfield on the satellites can be minimized by using non-ferromagneticmaterials such as aluminum wherever possible. These features, inaddition to the use of the solar panels to provide a moment about therotational axis, will suffice to at least reduce the rate of decay ofthe satellites' angular velocity.

As mentioned above, some or all of the above passive means forcontrolling satellite movement can be employed in the tumbling satelliteembodiment. That is, in one variation one or more solar panels can havesolar cells on only one side to impart an unbalanced moment on thesatellite to cause it to continue to tumble. Another variation couldlocate ferromagnetic materials in selected locations on the satellitethat will produce forces that vary in magnitude and direction as thesatellite traverses the earth's magnetic field.

Since satellites originally deployed to rotate will likely remain inorbit even if their initial angular velocity decays over time, they willstill be available as nodes in a radio route between ground stations.Since satellites in accordance with the present system are inexpensiveto construct, launch, and deploy, additional rotating satellites can belaunched to replace any whose angular velocity has decayed. This willnot only increase the number of satellites available for route creation,but to the extent that any of the older satellites remain spinning, theeffect will be to automatically take advantage of the improvedperformance made capable by using satellites rotating at differentangular velocities.

V. HIGH-GAIN DIRECTIONAL ANTENNAS FOR THREE-DIMENSIONAL RADIO MESHSYSTEMS

As discussed above, an important factor in establishing beam matcheswith satellites is the width of the radio beam transmitted from asatellite and received by another node (satellite or ground station).Rotating satellites would increase to some degree the probability of abeam match with satellites equipped with antennas having narrower beams(lower HPBW) than those discussed above in section IL However, atrade-off is still required between using antennas with narrower beamsand higher gains to increase the quality of radio links between nodes,and using antennas that produce broader beams (higher HPBW) with lowergains to increase the probability of creating a beam match. Thesituation is made more complex because the creation of beam matchesbetween system nodes depends on numerous other factors, such as thosediscussed previously, so that optimizing system performance entails morethan just a trade-off among competing antenna configurations. While itwill be well within the ability of one skilled in the art to design andimplement an operable system in accordance with the above-describedembodiments, such systems may prove to have certain performance issues,such as requiring inordinate amounts of time to assemble multipleacceptable radio links into a radio route between ground stations, whichin turn may delay call transmissions. While any potential drawbacks maybe acceptable in certain settings, such as where transmitting data overlong distances would otherwise not be possible, it would be preferableto assemble radio routes so that such delays are minimized oreliminated.

To that end, the present embodiment describes antenna designs andconfigurations that can further increase the probability of creatingsatellite-to-satellite and satellite-to-ground station beam matches byusing high-gain radio beams that will result in more rapidly creatingradio links with figures of merit acceptable for a radio route. It willbe appreciated that the same antenna configuration may also make itpossible to create a radio link between two ground stations where such alink would not be possible with lower gain, less highly directionalantennas. In addition, the antenna designs discussed here can be used inany of the satellite configurations and deployment schemes alreadydiscussed (such as rotating and counter-rotating satellites). They canalso be used in systems using non-orbital aerial nodes, in directcommunications between aerial nodes of different types, and withindividual personal devices such as smartphones and Wi-Fi equippedcomputers, described further below in section VI.

FIG. 7 is a schematic depiction of the surface of a substantiallyspherical satellite SX that exemplifies the present embodiment. FIG. 7represents in two dimensions the three-dimensional surface of thesatellite, showing an array of satellite antenna modules SA thatsubstantially cover the surface of the satellite. In thisimplementation, there are 25 antenna modules numbered SA1 to SA25. Inthe portion of the satellite surface in FIG. 7, the entire antennaopening at the satellite surface is shown for antennas SA2, SA6, SA7,and SA12. The openings of the other antennas are partially shown, someof which are labeled in FIG. 7, such as, SA3, SA8, SA11, SA13, and SA18.It will be understood that this is an idealized representation, intendedto indicate that it is preferable to make the satellite as small aspossible consistent with the inclusion of the desired number of antennasas well as providing sufficient spacing between antenna openings atappropriate locations to mount solar panels 14 (see FIGS. 3 and 4).

To increase antenna gain, the antenna reflectors in the presentembodiment are made as large as possible consistent with the otheroverall requirements of the system, such as limiting satellite weightand size to minimize launch costs. According to known principles ofparabolic antenna design, the reflector should be at least onewavelength in diameter, preferably more. Using the example given above,the antennas transmit (and receive) in the microwave C band at 5 GHzsignals. However, to facilitate comparison with the embodiment discussedin section II, take an example in which the antenna reflectors use 24 cmreflectors, which is 1.6 times the size of the reflectors in the sectionII embodiment. This could result in an increase of as much 250% in gain(which is proportional to the square of the reflector diameter=1.6²),but all things being equal it would reduce HPBW by only about 60%(1/1.6, per equation 1). If the feeds are located four wavelengths fromthe antenna reflectors, it is believed that a satellite with a diameterof about one meter (or comparable size if the satellite is nonspherical)will be able to meet the operational specifications herein. However, itwill be understood that operation of the system does not rely on using aparticular antenna design, and those skilled in the art will be able touse known antenna design principles to provide a satellite with thecapabilities required by the present embodiment. Nevertheless, antennaswith larger reflectors can be used to provide even higher gains, and thesatellites can be made correspondingly larger. Moreover, the amount ofadded weight will for the most part be attributable to the increase inthe size of the satellite outer casing and the additional materialneeded for the additional feeds and larger reflectors (althoughsatellite weight can be reduced if the reflectors have a meshconstruction). Accordingly, satellites used in the present embodimentshould still be extremely light in comparison to known communicationssatellites for all of the reasons already discussed above, a principalone among them being that they require no attitude control.

In the present embodiment illustrated in FIG. 7 each of the antennas SA1to SA25 is a parabolic antenna with seven feeds F1 to F7. The followingdescription uses the notation FX_(SAX) to denote a particular feed of aparticular antenna. For example, F1 _(SA3) refers to the feed F1 of theantenna SA3, F5 _(SA18) refers to the feed F5 of the antenna SA18, andso forth. The feeds F1 to F6 are spaced equidistant from each other andare arranged at a distance from the feed F7 at the antenna focal point,for reasons discussed in more detail below. The shape and curvature ofthe antenna reflectors can be chosen according to known multi-feedantenna designs and principles of operation. The hexagonal shape of theantenna openings is used in the figure to emphasize that the feeds F2 toF7 are displaced from the reflector focal axis. It will also beappreciated that the antenna reflectors can have non-parabolictopologies, such as spherical, combination spherical/parabolic, andothers, to maximize the operational characteristics of the systemembodiment described here. Examples of multi-feed reflecting antennadesigns that those skilled in the art will be able to adapt for use inthe present embodiment are disclosed in U.S. Pat. No. 3,815,140, U.S.Pat. No. 6,208,312, U.S. Pat. No. 6,219,003, and U.S. Pat. No.9,035,839, the disclosures of all of which are incorporated herein byreference as if set out in full. It should be understood that the numberof antennas and the number of feeds per antenna depends on the design ofthe satellites and the desired operational characteristics of thesystem. More or fewer antennas and feeds may be used within the scope ofthe present invention.

A. Antenna Control Circuitry

FIG. 8 is a functional block diagram of exemplary computer circuitry forprocessing routing signals and calls received by the antenna feeds andfor assembling linking signals and calls for transmission by the antennafeeds. As with all of the descriptions of computer and processingcircuitry previously described, the boxes and the connections betweenthem in FIG. 8 are used solely as an aid in explaining the operation ofthe present embodiment. It will be well within the skill of the art todesign and implement appropriate computer components, includinghardware, firmware, and/or software, as required to perform thefunctions described herein. Moreover, the circuit diagram in FIG. 8 isnot meant to suggest any particular architecture for performing thefunctions to be described.

FIG. 8 depicts just the antenna modules SA1 and SA25 for purposes of thepresent description; the remaining antenna modules are omitted from thefigure for clarity. Each antenna module has associated with it amicroprocessor “μproc” for processing signals introduced to the antennafeeds and receiving signals from the antenna feeds. The individualantenna microprocessors are identified in FIG. 8 by the notation μproc(SAX), “X” being the number of the associated antenna module accordingto the description above of FIG. 7. Thus, in the figure, “μproc (SA25)”denotes the onboard circuitry for processing signals introduced to andreceived from the feeds F1 to F7 of the antenna module SA1. Likewise,“μproc (SA25)” denotes the onboard circuitry for processing signalsintroduced to and received from the feeds F1 to F7 of the antenna moduleSA25. Each of the other antenna modules SA2 to SA24 is associated withits own microprocessor, as represented by the plural dots between μproc(SA1) and μproc (SA25) in FIG. 8. Each microprocessor μproc includesradio transceivers denoted by R1 to R7, indicating that each isassociated with a corresponding feed F1 to F7 of that antenna. Thetransceivers convert RF signals received by the feeds into a data streamand convert a data stream into RF signals to be broadcast by theantenna.

The antenna module microprocessors are connected by power and data lines40 _(SA1) to 40 _(SA25) to a satellite CPU 40′. The dots in FIG. 8between the lines 40 _(SA1) and 40 _(SA25) indicate that like power anddata lines also connect corresponding power and data lines to eachantenna module microprocessor μproc (SA2) to μproc (SA24). Thereferences used for the power and data lines and the satellite CPU hereecho those shown in FIG. 4 to indicate that components identified bysimilar references function to perform route creation and datatransmissions similar to those of their like-referenced counterparts inFIG. 4, as discussed now.

B. Route Creation and Data Transmission

In general, radio routes are created as discussed above in section IIIA.However, the use of multiple feeds for each satellite antennanecessitates identifying not only a particular satellite antenna for agiven radio route, but also the individual feed of that antenna. Forexample, in one method of creating radio routes with a system accordingto the present embodiment, routing messages will include information onthe antenna feed of the particular antenna, rather than just the antennaitself. This description will use as an example the creation of a radioroute between two ground stations via a single satellite, discussedabove in section III and depicted in FIG. 5. The ground station nodescan either have multi-feed antennas similar to the satellite nodes, orbe constructed the same as in the embodiment associated with FIG. 5 withonly a single feed per antenna. In either case, the ground station nodescan use larger and/or more antennas than the satellite nodes because theground stations do not have the same size and weight constraints.However, a ground station node only requires antennas arranged fortransmitting and receiving signals around a 180° sphere (that is, itsantennas need only point “up” and “out” to provide coverage of the skyabove the ground station).

Referring to the discussion accompanying Table 1, ground nodes send outrouting signals with the initial information identified in Table 1. Oneor more satellites receive these signals on their antennas, but in thepresent embodiment the antenna module microprocessors μproc (SA) foreach antenna module that receives a signal identifies both theparticular antenna(s) that received signals from ground stations and theantenna feed on which the signals were received. The next steps in therouting process are analogous to the steps discussed in connection withTables 2 and 3 above, in which all of the antennas of all of thesatellites that have received initial information signals from a groundstation broadcast a routing signal. However, in the present embodimentall of the feeds in all of the antennas broadcast the routing signal.

As seen in FIG. 7, the satellite antenna feeds are numbered to indicatethat similar numbered feeds transmit routing signals in similar timeslots. Likewise, similarly numbered feeds are disposed in the samelocation relative to the antenna reflector in all of the antennas inorder to maximize the angular separation between like numbered feeds ofadjacent antennas. Put another way, corresponding feeds of the satelliteantennas are disposed in the substantially the same angular orientationrelative to the antenna reflector in order to transmit at substantiallythe same angle relative to an axis of the antenna. Thus, the narrowradio beams from similarly numbered feeds can be broadcastsimultaneously with virtually no chance that they will interfere witheach other or be received at the same node. As a result, all of theantenna feeds in a node can transmit in the same time slot. For example,all of the antennas SA1 to SA25 would transmit from their F1 feeds atthe same time, then all of the antennas would transmit from their F2feeds at the same time, and so forth. This results in seven differenttime slots for each route creation cycle. In addition, all of the feedsare disposed on an imaginary surface with substantially the sametopology as the antenna's reflecting surface. (For example, if theantenna has a parabolic reflector, the imaginary surface is also aparabola.) Accordingly, the present embodiment only needs seven timeslots to broadcast routing signals from all of the antenna feeds, asopposed to 25 time slots as in the above embodiment using 25 single-feedantennas. This further increases the probability of rapidly creating aradio route between two ground stations.

Because of the increased spatial density of the antenna feeds, at leastsome of the incoming routing signals may be received by more than onefeed. The individual antenna microprocessors μproc identify the feedthat will provide the highest quality radio link if that antenna modulewere used in a radio route. This can be done using any of the criteriaalready discussed above. This information is passed on to the satelliteCPU 40′, via the power and data lines 40 _(SA1) to 40 _(SA25), whichthen performs its own evaluation of all of the radio signals selected bythe individual antenna microprocessors. The same procedure is followedwhen an incoming radio signal from another node (in this example, groundstation no. 1000) is received by feeds in bordering antenna modules. Forexample, an incoming initial information signal might be received byfour feeds in adjoining antenna modules, such as F3 _(SA2), F4 _(SA2),F1 _(SA7), and F6 _(SA7). In that case, the microprocessor μproc (SA2)would determine which of its feeds F3 or F4 would provide the betterradio link, and provide the determinative parameters supporting thatdecision to the satellite CPU 40′. Likewise, the microprocessor μproc(SA7) would determine which of its feeds F1 or F6 would provide thebetter radio link, and provide the determinative parameters supportingthat decision to the satellite CPU 40′. The satellite CPU then uses allof the data received from the antenna modules to identify the antennamodule and its feed to include in the routing signals sent from all of175 antenna feeds. Radio routes are then identified between groundstations in accordance with the discussion accompanying FIG. 5.

Data transmissions proceed as described above in section IIIB. Withoutrepeating the entire data transmission process from that section, thebasic concept is that a data communication comprising packets of datawith a header and a payload is received at an originating groundstation. The header will typically include address information,including identification of the destination ground station. The datatransmission module unpacks the address information and indicates thesystem address (node number) of the destination node. The packets willthen be sent to the destination ground station over the radio routeestablished in the manner described above.

In a variation of the process, the routing messages sent between thenodes do not include antenna feed information. That is, they areessentially the same as in the route creation process described inassociation with Tables 2 and 3 above. In this adaptation, thesatellites store the antenna feed associated with a particular receivingantenna. For example, in Table 2, if the satellite node no. 250 receivedthe routing signal on feed F7 of receiving antenna SA6, the satellitewould store that information on board. Then, if the route for a datatransmission to ground node 1000 included the antenna SA6 in satelliteno. 250, the satellite would broadcast it using feed F7 of that antenna.

The following is a summary of steps involved in creating an inter-nodalradio route for data transmissions pursuant to one exemplary applicationof the present embodiment:

-   1. A first node N1 transmits a first routing message from a    plurality of its antennas.-   2. The first routing message from node N1 may be received by at    least two different nodes N2 and N3.-   3. Node N2 may hear the first routing message on more than one feed    of a first antenna and/or on more than one feed of a second antenna.-   4. If so, node N2 determines the feed with the highest quality    signal in the first antenna and the feed with the highest quality    signal in the second antenna.-   5. Node N2 then compares the signal quality as between the first and    second antennas, and selects the antenna with the better quality    signal.-   6. Then node N2 transmits a second routing message including its    identity (“N2”), the identity of node N1, and the signal quality    between node N1 and node N2.-   7. Node N3 may also receive the first routing message on more than    one feed of a first antenna and/or on more than one feed of a second    antenna; if so, node N3 then compares the signal quality between the    first and second antennas, and selects the antenna with the better    quality signal.-   8. Then node N3 transmits a third routing message including its    identity (“N3”), the identity of node N1, and the signal quality    between node N1 and node N3.-   9. A node N4 that receives the first and second routing messages    thus knows the higher quality radio route (via either node N2 or N3)    to node N1.-   10. Calls (data transmissions) received by the node N4 for    transmission to node N1 are directed accordingly to the node N2 or    the node N3, which in turn transmits the call to node N1 using the    antenna feed identified in step 5 (node N2) or in the antenna feed    identified step 7 (node N3).

It will be appreciated that in this example, the node N1 can represent adestination ground station or an intermediate node that links withanother satellite node. Likewise, the node N4 can represent anoriginating ground station or an intermediate node that links withanother satellite. It should also be understood that the above steps arepresented as one way of creating a radio route between nodes in a systemaccording this embodiment. It will not be applicable in all instances.For example, a given satellite antenna feed may receive a routingmessage of insufficient quality to pass a threshold test and thus berejected by the processing circuitry in the satellite as suitable foruse in a radio route.

C. Summary

By using larger satellite antennas the present embodiment increases thegain of routing signals transmitted from the satellites by a multipleproportional to the square of the increase antenna diameter, but onlydecreases the antenna HPBW by an amount proportional to the diameteritself. At the same time, each of the antennas has multiple feeds, whichin effect multiplies the number of satellite antennas available forroute creation by the number of feeds in each antenna. In the exemplarysatellite depicted in FIG. 7 the effective number of antennas is 125. Itwill be appreciated that providing satellites with route creationcapabilities approaching those achieved by this embodiment would requirethe same number of single-feed antennas with the same size. Sincecorresponding disposed feeds of different antennas can broadcast routingmessages in the same time slot, only seven time slots are needed foreach route-creation cycle, rather than 25 as in the embodiment with 25single-feed antennas. This will decrease the time it takes to establishroutes.

A satellite with 125 single-feed antennas capable of broadcasting andreceiving radio signals at comparable gains and beam widths wouldrequire 100 additional single-feed antennas. Such a system would bewithin the scope of the present invention in its broadest aspects, butit would obviate many important objects of the invention. One of thoseobjects is to provide a system in which the satellites are so small andlightweight that the cost of launching is minimal. One way launch costscan be minimized is to launch multiple satellites on a single vehicle.Larger and heavier satellites require more launches than smaller,lighter ones. While the present embodiment using multi-feed antennaswill typically use satellites that will be larger and slightly heavierthan the single-feed embodiment discussed further above, they will stillbe orders of magnitude smaller and lighter than a satellite havingenough single-feed antennas to achieve the same functionality. Inaddition, increasing by several-fold the number of routing signals sentfrom each satellite will likely increase the probability of creatingradio links with ground stations and other satellites, which couldreduce the number of satellites required to achieve the same results asusing satellites with single-feed antennas, thus bringing down the costof deployment of a system in accordance with the present embodiment.

In addition, ground nodes with multi-feed antennas will also enhancecommunications directly between them. For example, depending on theterrain served by a system according to the present embodiment, suitablealgorithms in the system nodes (satellites and ground stations) mayassemble a radio route between two particular ground stations withoutinvolving any of the satellites. Moreover, such nodes could be used toenhance the operability of purely ground-based radio mesh systems suchas those disclosed in the inventor's U.S. Pat. No. 5,793,842 and U.S.Pat. No. 6,459,899. Nodes capable of producing high gain beams over acertain spherical extent would find utility in cities with tallbuildings, which could include nodes capable of directing radio beamstoward the ground. Another example would be cities that include highhills and valleys, such as the Los Angeles area.

In ground node-to-node communication systems, city-wide bandwidth can beconserved by the use of very narrow beams created by multi-feed antennassuch as those characterizing the present embodiment. These higher gainantennas would also provide better received signal strength. Although amulti-feed antenna system will require additional radio transceivers,making cost a consideration, it is possible that a hemispherical designcould be used facing round side up in valleys and round facing side downin higher elevations to reduce the number of antennas required in agiven node.

VI. OTHER AERIAL NODE EMBODIMENTS FOR THREE-DIMENSIONAL RADIO MESHSYSTEMS

As already pointed out, implementation of the three-dimensional radiosystem described herein is not limited to using satellites in low-earthorbits of approximately 500 miles or so. In one variation, satellites invery low earth orbits, in the range of 100-200 miles, can be utilized toincrease the strength of radio signals reaching the ground. In addition,non-orbiting aerial nodes can also be used in the systems describedherein. For example, nodes similar in construction to the satellitesdescribed above can be suspended from balloons that are allowed to driftfreely in the stratosphere (or at lower altitudes). The balloon-mountednodes would include antennas corresponding to the satellite antennasdescribed above arranged in the nodes for transmitting and receivingsignals in plural directions. Another variation could mount such nodeson unmanned aerial vehicles (“drones”) deployed randomly over aparticular area. It is believed that such a system would enablecommunications directly from hand-held devices or other personal devicesmore readily than a satellite-based system because the drones would becloser to the ground stations (hand-held devices) than in a satellitenode system.

Any one of the above variations on the low-earth orbit satellites can beused independently, or in combinations of two or more such variations.FIG. 9 illustrates some of these variations. In the figure, low earthorbit satellites SLO₁ and SLO₂ represent a large plurality of suchsatellites, which have no attitude control such as the satellitesdiscussed in detail above. Also represented in FIG. 9 are very low earthorbit satellites SVLO₁, SVLO₂, SVLO₃, etc., which represent a largeplurality of such satellites without attitude control. These satellitescould be used to support the so-called “Internet of Things” (IoT), whichis generally taken to mean inter-networked physical devices, vehicles(also referred to as “connected devices” and “smart devices”),buildings, and other items embedded with electronics, software, sensors,actuators, and network connectivity which enable these objects tocollect and exchange data. Such IoT devices must connect directly toeach other, and the stronger signal strength from the low-flyingsatellites can increase the signal strength available at the earth'ssurface by up to 6 dB more than the satellites at higher altitudes.Further improvement in the operability of such a system can be achievedby using satellites with multi-feed antennas as described in theprevious embodiment.

Another alternative node type would be mounted on balloons BN₁, BN_(s),etc., permitted to float in the atmosphere high altitudes. The balloonsmay prove useful in providing communication services (Internet access,emails, etc.) to relatively small areas on the surface of the earth E.Google is testing a system it calls Project Loon to provide Internetaccess to rural and remote areas. According to reports, high-altitudeballoons are placed in the stratosphere at an altitude of about 18 km(11 miles) to create an aerial wireless network. The balloons aremaneuvered by adjusting their altitude in the stratosphere to float to awind layer after identifying the wind layer with the desired speed anddirection using published wind data. Signals travel through the balloonnetwork from balloon to balloon, then to a ground-based stationconnected to an Internet service provider (ISP), then onto the globalInternet. See, for example, “Project Loon,” Wikipedia,https://en.wikipedia.org/wiki/Project_Loon (last visited Sep. 20, 2017).One skilled in the art could easily adapt nodes such as those describedherein, including those with multi-feed antennas, as in the GoogleProject Loon system.

Another type of non-orbital aerial node could be mounted on drones DR₁,DR₂, etc. The drones could fly over prescribed areas at altitudes of1000-2000 feet, although other altitudes might be desirable depending onthe particular area to be serviced by the system. These nodes wouldpreferably use the multi-feed antenna embodiment described above toprovide a strong enough signal to enable direct communication withindividual hand-held devices HD, as indicated by the route in solidlines between the ground station GS₃ and the hand-held device HD via theballoon BN₂ and the drone DR₁. There might also be a route from theground station GS₂ to the hand-held device via the drone DR₁. FIG. 9also shows in single-dot-dash lines and double-dot-dash lines otherexemplary routes created using aerial nodes in accordance with thedescription herein. A route directly between two ground stations, inaccordance with the discussion further above, is depicted by a dashedline in the figure.

VII. OTHER MODIFICATIONS AND VARIATIONS

It will be appreciated that numerous variations and modifications of thestructures and methods described heretofore are possible within thescope of the present invention. The above exemplary embodiments useaddition of the figures of merit of two potential radio links to selecta preferred radio route. However, the invention encompasses other waysof determining a preferred route, since using the sums of the figures ofmerit for two different potential radio routes would favor a multiplesatellite route over a single satellite route. Thus, although additionof the figures of merit in a single satellite route will typicallyresult in an optimum or preferred route, more complex and sophisticatedalgorithms may be necessary to implement this aspect of the inventionwhen choosing between potential single- and multiple-satellite routes orbetween two potential multiple-satellite routes. One possible approachin those situations would be to select a particular route when otherpotential routes would include a link judged to be inferior for one ormore reasons, some examples of which are discussed above (inadequatesignal strength and/or excessive error rate between various nodes in apotential multiple satellite route, low remaining satellite batterylife, excessive link loading, or eliminating potential links withfigures of merit below a predetermined threshold).

Those skilled in the art will recognize that “figure of merit” asdiscussed herein is simply one way of articulating the important conceptof choosing a radio route deemed to be optimum for data communicationsbetween two ground stations. The parameters used in determining a figureof merit for a particular potential link are not limited to thosespecifically pointed out in this description. One example would takeinto account that the satellites are moving relative to each other, sothat the quality of potential links between satellites or between asatellite and a ground station will change over time. Thus, one of thefactors in selecting a link could be the derivative of link quality(figure of merit) with respect to time, since a positive value wouldindicate that the link quality would increase and thus be more stable,while a negative value would indicate the opposite.

VII. SUMMARY AND CONCLUSION

Those skilled in the art will readily recognize that only selectedpreferred embodiments of the invention have been depicted and described,and it will be understood that various changes and modifications can bemade other than those specifically mentioned above without departingfrom the spirit and scope of the invention, which is defined solely bythe claims that follow.

What is claimed is:
 1. A method for creating a radio communication routefor data communications to a sending ground station from a receivingground station different from the sending ground station, wherein theground stations include a plurality of ground station directionalantennas for transmitting and receiving radio signals, the methodcomprising: (a) providing multiple satellites orbiting the earth,wherein each of a plurality of the satellites includes a plurality ofsatellite antennas and each of multiple antennas of the plurality ofsatellite antennas comprises a reflector with a plurality of feeds fortransmitting radio signals in a corresponding plurality of directionsdifferent from each other and for receiving radio signals in therespective different directions; (b) receiving on at least one of themultiple antennas of plural receiving satellites an initial informationrouting signal transmitted from an antenna at a sending ground station;(c) storing at the plural satellites receiving the initial informationrouting signal on at least one of the multiple antennas (i) addressinformation identifying the ground station from which the initialinformation routing signal was received, (ii) the satellite antenna onwhich the initial information routing signal was received, and (iii) theantenna feed on which the information routing signal was received; (d)transmitting linking information routing signals from a number of theantennas of each of the plural receiving satellites, wherein the linkinginformation routing signals include (i) linking information identifyingeach of the plural receiving satellites, and (ii) a quality of thereceived initial information routing signal indicating a suitability ofthe satellite and the sending ground station as a radio link in a radiocommunication route between the ground stations; (e) storing at areceiving ground station receiving at least one linking informationrouting signal (i) address information identifying the satellitetransmitting the linking information routing signal, (ii) the receivingground station antenna on which the linking information routing signalwas received, and (iii) a quality of the initial information routingsignal received at the satellite transmitting the linking informationrouting signal; and (f) determining a preferred radio communicationroute for data communications from the receiving ground station to thesending ground station via a particular satellite based on (i) a qualityof the received linking information routing signal indicating asuitability of the receiving ground station and the particular satelliteas a radio link in a radio communication route between the groundstations, and (ii) the quality of the initial information routingsignal, wherein the routing signals comprise digital data streams andthe quality of a received routing signal is expressed as a quantitativefigure of merit based at least in part on a property of the digital datastream.
 2. A method as in claim 1, wherein the satellites are designatedas a first type of node and the ground stations are designated as asecond type of node, and each type of node can only communicate with anode of a different type.
 3. A method as in claim 2 further includingsending a data transmission from the receiving ground station to thesending ground station, wherein the first type of node only transmitsradio signals in a first mode and only receives radio signals in asecond mode that substantially eliminates interference withtransmissions in the first mode, and the second type of node onlyreceives radio signals in the first mode and only transmits radiosignals in the second mode.
 4. A method as in claim 1, wherein all ofthe plurality of satellite antennas comprise a reflector with aplurality of feeds for transmitting radio signals in a correspondingplurality of directions different from each other and for receivingradio signals in the respective different directions.
 5. A method as inclaim 4, wherein respective feeds of each of the multiple satelliteantennas are disposed in substantially the same angular orientationrelative to the antenna reflector for transmitting radio signals atsubstantially the same angle relative to an axis of the antenna.
 6. Amethod as in claim 5, wherein each antenna reflector of the multiplesatellite antennas has a parabolic cross section and is circular with adiameter at least 4 times the wavelength of the radio signals (γ) andeach feed is spaced from the reflector at least 4 times γ.
 7. A methodas in claim 1, wherein the reflector of each of the multiple satelliteantennas has a parabolic cross section and includes at least sevenfeeds, one of which is disposed substantially at the focal point of theparabolic reflector and the remaining feeds are distributed equallyaround the focal point and spaced radially from the focal point.
 8. Amethod as in claim 1, wherein the multiple satellite antennas arearranged to transmit and receive radio signals over substantially theentire spherical space surrounding each of the satellites.
 9. A methodas in claim 1 further including communicating a data transmissioncomprising packets of digital data from an origin comprising a receivingground station to a destination comprising a sending ground station,each data transmission packet including a header including the addressinformation of the destination and a payload including a data streamrepresenting the content of the transmission, wherein: the origintransmits the packet of digital data to the particular satellite usingthe receiving ground station antenna on which the linking informationrouting signal was received; and the particular satellite transmits thepacket of digital data transmission to the destination using the feed ofthe antenna of the particular satellite on which the initial informationrouting signal was received.
 10. A method as in claim 1, whereindetermining a preferred radio communication route for datacommunications from the receiving ground station to the sending groundstation is performed by the receiving ground station without a centralcomputer communicating with the satellites or other ground stations. 11.A method as in claim 1, further comprising deploying the satellites witha rotational velocity about an axis of rotation.
 12. A method as inclaim 11, wherein a predetermined plurality of the satellites rotate ina first direction about a rotational axis and a second predeterminedplurality rotate in a second direction about a rotational axis.
 13. Amethod as in claim 12, wherein predetermined numbers of the satellitesrotate in opposite directions.
 14. A method as in claim 11, wherein thesatellites occupy random orbits.
 15. A method as in claim 14, whereinthe satellites orbit the earth without an attitude control mechanismcomprising moving parts for changing the angular orientation of thesatellites.
 16. A method as in claim 14, wherein the satellites tumbleas they orbit the earth without regard to the angular orientation of thesatellites.
 17. A method as in claim 1, wherein the satellites occupyrandom orbits.
 18. A method as in claim 17, wherein the satellites orbitthe earth without an attitude control mechanism comprising moving partsfor changing the angular orientation of the satellites.
 19. A method asin claim 17, wherein the satellites tumble as they orbit the earthwithout regard to the angular orientation of the satellites.
 20. Amethod as in claim 1, wherein the antenna reflectors and feeds are fixedin position on the satellites.
 21. A method as in claim 20, wherein thesatellites occupy random orbits.
 22. A method as in claim 21, whereinthe satellites orbit the earth without an attitude control mechanismcomprising moving parts for changing the angular orientation of thesatellites.
 23. A method for creating a radio communication route fordata communications from a receiving ground station to a sending groundstation, wherein the ground stations include a plurality of groundstation directional antennas for transmitting and receiving radiosignals, the method comprising: (a) providing multiple satellitesorbiting the earth, wherein each of a plurality of the satellitesincludes a plurality of satellite antennas and each of multiple antennasof the plurality of satellite antennas comprises a reflector with aplurality of feeds for transmitting radio signals in a correspondingplurality of directions different from each other and for receivingradio signals in the respective different directions; (b) receiving onat least one of the multiple antennas of at least one satellite aninitial information signal transmitted from an antenna at a sendingground station; (c) storing at any satellite receiving the initialinformation signal on at least one of the multiple antennas at least (i)address information identifying the ground station from which theinitial information signal was received, (ii) the satellite antenna onwhich the initial information signal was received, and (iii) the antennafeed on which the information signal was received; (d) transmittinglinking information signals from a number of the antennas of at leastone satellite receiving the initial information signal, wherein thelinking information signals include (i) linking information identifyingthe satellite, and (ii) a quality of the received initial informationsignal indicating a suitability of the satellite and the sending groundstation as a radio link in a radio communication route between theground stations; (e) storing at a receiving ground station receiving atleast one linking information signal (i) address information identifyingthe satellite transmitting the linking information signal, (ii) thereceiving ground station antenna on which the linking information signalwas received, and (iii) a quality of the initial information signalreceived at the satellite transmitting the linking information signal;and (f) determining a preferred radio communication route for datacommunications from the receiving ground station to the sending groundstation via a particular satellite based on (i) a quality of thereceived linking information signal indicating a suitability of thereceiving ground station and the particular satellite as a radio link ina radio communication route between the ground stations, and (ii) thequality of the initial information signal, wherein: the satellites aredesignated as a first type of node and the ground stations aredesignated as a second type of node, and each type of node can onlycommunicate with a node of a different type, and the method furtherincludes sending a data transmission from the receiving ground stationto the sending ground station, wherein the first type of node onlytransmits radio signals in a first mode and only receives radio signalsin a second mode that substantially eliminates interference withtransmissions in the first mode, and the second type of node onlyreceives radio signals in the first mode and only transmits radiosignals in the second mode.
 24. A method as in claim 23, wherein: all ofthe plurality of satellite antennas comprise a reflector with aplurality of feeds for transmitting radio signals in a correspondingplurality of directions different from each other and for receivingradio signals in the respective different directions; and respectivefeeds of each of the multiple satellite antennas are disposed insubstantially the same angular orientation relative to the antennareflector for transmitting radio signals at substantially the same anglerelative to an axis of the antenna.
 25. A method as in claim 24, whereineach antenna reflector of the multiple satellite antennas has aparabolic cross section and is circular with a diameter at least 4 timesthe wavelength of the radio signals (γ) and each feed is spaced from thereflector at least 4 times γ.
 26. A method as in claim 23, wherein thereflector of each of the multiple satellite antennas has a paraboliccross section and includes at least seven feeds, one of which isdisposed substantially at the focal point of the parabolic reflector andthe remaining feeds are distributed equally around the focal point andspaced radially from the focal point.
 27. A method as in claim 23,wherein the multiple satellite antennas are arranged to transmit andreceive radio signals over substantially the entire spherical spacesurrounding each of the satellites.
 28. A method as in claim 23, whereindetermining a preferred radio communication route for datacommunications from the receiving ground station to the sending groundstation is performed by the receiving ground station without a centralcomputer communicating with the satellites or other ground stations. 29.A method as in claim 23, wherein the satellites occupy random orbits.30. A method as in claim 29, wherein the satellites orbit the earthwithout an attitude control mechanism comprising moving parts forchanging the angular orientation of the satellites.
 31. A method as inclaim 23, wherein the satellites orbit the earth without an attitudecontrol mechanism comprising moving parts for changing the angularorientation of the satellites.
 32. A method as in claim 23, wherein thesatellites tumble as they orbit the earth without regard to the angularorientation of the satellites.
 33. A method as in claim 23, wherein theantenna reflectors and feeds are fixed in position on the satellites.34. A method for creating a radio communication route for datacommunications from a receiving ground station to a sending groundstation, wherein the ground stations include a plurality of groundstation directional antennas for transmitting and receiving radiosignals, the method comprising: (a) providing multiple satellitesorbiting the earth, wherein each of a plurality of the satellitesincludes a plurality of satellite antennas and each of multiple antennasof the plurality of satellite antennas comprises a reflector with aplurality of feeds for transmitting radio signals in a correspondingplurality of directions different from each other and for receivingradio signals in the respective different directions; (b) receiving onat least one of the multiple antennas of at least one satellite aninitial information signal transmitted from an antenna at a sendingground station; (c) storing at any satellite receiving the initialinformation signal on at least one of the multiple antennas at least (i)address information identifying the ground station from which theinitial information signal was received, (ii) the satellite antenna onwhich the initial information signal was received, and (iii) the antennafeed on which the information signal was received; (d) transmittinglinking information signals from a number of the antennas of at leastone satellite receiving the initial information signal, wherein thelinking information signals include (i) linking information identifyingthe satellite, and (ii) a quality of the received initial informationsignal indicating a suitability of the satellite and the sending groundstation as a radio link in a radio communication route between theground stations; (e) storing at a receiving ground station receiving atleast one linking information signal (l) address information identifyingthe satellite transmitting the linking information signal, (ii) thereceiving ground station antenna on which the linking information signalwas received, and (iii) a quality of the initial information signalreceived at the satellite transmitting the linking information signal;and (f) determining a preferred radio communication route for datacommunications from the receiving ground station to the sending groundstation via a particular satellite based on (i) a quality of thereceived linking information signal indicating a suitability of thereceiving ground station and the particular satellite as a radio link ina radio communication route between the ground stations, and (ii) thequality of the initial information signal, the method further includingcommunicating a data transmission comprising packets of digital datafrom an origin comprising a receiving ground station to a destinationcomprising a sending ground station, each data transmission packetincluding a header including the address information of the destinationand a payload including a data stream representing the content of thetransmission, wherein (1) the origin transmits the packet of digitaldata to the particular satellite using the receiving ground stationantenna on which the linking information signal was received, and (ii)the particular satellite transmits the packet of digital datatransmission to the destination using the feed of the antenna of theparticular satellite on which the initial information signal wasreceived.
 35. A method as in claim 34, wherein: all of the plurality ofsatellite antennas comprise a reflector with a plurality of feeds fortransmitting radio signals in a corresponding plurality of directionsdifferent from each other and for receiving radio signals in therespective different directions; and respective feeds of each of themultiple satellite antennas are disposed in substantially the sameangular orientation relative to the antenna reflector for transmittingradio signals at substantially the same angle relative to an axis of theantenna.
 36. A method as in claim 35, wherein each antenna reflector ofthe multiple satellite antennas has a parabolic cross section and iscircular with a diameter at least 4 times the wavelength of the radiosignals (γ) and each feed is spaced from the reflector at least 4 timesγ.
 37. A method as in claim 34, wherein the reflector of each of themultiple satellite antennas has a parabolic cross section and includesat least seven feeds, one of which is disposed substantially at thefocal point of the parabolic reflector and the remaining feeds aredistributed equally around the focal point and spaced radially from thefocal point.
 38. A method as in claim 34, wherein the multiple satelliteantennas are arranged to transmit and receive radio signals oversubstantially the entire spherical space surrounding each of thesatellites.
 39. A method as in claim 34, wherein determining a preferredradio communication route for data communications from the receivingground station to the sending ground station is performed by thereceiving ground station without a central computer communicating withthe satellites or other ground stations.
 40. A method as in claim 34,wherein the satellites occupy random orbits.
 41. A method as in claim40, wherein the satellites orbit the earth without an attitude controlmechanism comprising moving parts for changing the angular orientationof the satellites.
 42. A method as in claim 34, wherein the satellitesorbit the earth without an attitude control mechanism comprising movingparts for changing the angular orientation of the satellites.
 43. Amethod as in claim 34, wherein the satellites tumble as they orbit theearth without regard to the angular orientation of the satellites.
 44. Amethod as in claim 34, wherein the antenna reflectors and feeds arefixed in position on the satellites.